WO2002044372A2 - Nucleotide and protein sequence of helios 3 and methods of use - Google Patents

Abstract

Specific Helios isoforms, as well as the correlation of the presence of the specific Helios isoforms and other non-functional Helios isoforms with lymphoid cell abnormalities is provided in the invention. Methods for detecting and treating lymphoid cell abnormality, including hematoloic malignancy, are also provided.

Description

NUCLEOTIDE AND PROTEIN SEQUENCE OF

HELIOS 3 AND METHODS OF USE

This application is being filed as a PCT International Patent Application in the name of Parker Hughes Institute, a U.S. national corporation and resident,

(Applicant for all countries except US); Lei Sun, a Chinese citizen and U.S. resident (Applicant for US only); Hoshnuwar Kerawalla, an Indian citizen and U.S. resident (Applicant for US only); and Fatih M. Uc un, a U.S. citizen and resident (Applicant for US only), on 20 September 2001, designating all countries and claiming priority to U.S. Serial No. 60/250,622 filed 01 December 2000.

Field of the Invention

This invention relates to protein isoforms of Helios, and to nucleic acid sequences encoding Helios, useful in the diagnosis of hematologic malignancy, particularly lymphoid malignancy, including stem cell leukemia and T-cell and B- cell acute lymphoblastic leukemia (ALL).

Background of the Invention

Acute lymphoblastic leukemia (ALL) is the most common form of cancer in children. Leukemic clones in ALL patients are thought to originate from normal lymphocyte precursors arrested at various stages of T- or B-lymphocyte development, hence, any critical regulatory network that controls normal lymphocyte development is a potential target for a leukemogenic event.

The development of a functional immune system by coordinated expression of genes controlling lineage commitment, proliferation, and differentiation of lymphocyte precursors is tightly regulated. As master regulators of lymphocyte ontogeny, Ikaros, Aiolos, and Helios, members of the Kruppel family of "zinc finger" DNA-binding proteins, ensure the orderly differentiation of lymphocyte precursors (Georgopoulos et al., 1992, Science 258: 808-812; Georgopoulos et al., 1994, Cell 79: 143-156; inandy et al., 1995, Cell 83: 289-299; Wang et al., 1996, Immunity 5: 537-549; Wang et al., 1998, Immunity 9: 543-553; Morgan et al, 1997, EMBO J. 16: 2004-2013; Kelley et al., 1998, Curr Biol. 8: 508-515; Hahm et al, 1998, GeneDev. 12: 782-796; Hosokawa et al., 1999, Immunogenetics 50: 106- 108). This group of transcription factors are thought to function both as transcription activators and repressors to regulate gene expression as required during discrete stages of lymphocyte ontogeny (Molnar et al., 1994, Mol Cell Biol 14:

8292-8303; Sun et al., 1996, EMBOJ. 15: 5358-5369; Brown et al., 1997, Cell 91:

845-854; Koipally et al., 1999, EMBO J. 18: 3090-3100; Koipally et al., 2000, JBiol Chem 275:19594-602; Kim et al., 1999, Immunity 10: 345-355; Brown et al., 1999,

Mol Cell 3: 207-217).

Alternatively spliced transcripts of the Ikaros gene encode at least eight zinc finger proteins (Ikaros isoforms Bc-l through Ik-8) with distinct DNA binding capabilities and specificities (Molnar et al, 1994, Mol Cell Biol 14: 8292-8303; Sun et al., 1996, EMBO J. 15: 5358-5369). Ikaros proteins are highly conserved between human and mouse, and share a common carboxy-terminal domain containing a bipartite transcription activation motif and two zinc finger motifs required for hetero- and homodimerization among the Ikaros isoforms and interactions with other proteins (Sun et al., 1996, EMBO J. 15: 5358-5369; Molnar et al., 1996, J Immunol 156: 585-592). Ikaros isoforms differ in their amino-terminal zinc finger (FI through F4) composition and in their overall DNA binding and transcriptional activation properties (Molnar et al., 1994, Mol Cell Biol 14: 8292-8303). At least three amino-terminal zinc fingers are required for high affinity DNA binding to the four base pair core motif GGGA. Thus, only the isoforms Ik-1, Ik-2, and Ik-3, which contain three or more N-terminal zinc fingers, exhibit high affinity DNA binding (Molnar et al., 1994, Mol Cell Biol 14: 8292-8303). These DNA binding isoforms localize to the nucleus, whereas isoforms Ik-4 through Ik-8, which have fewer than three amino-terminal zinc fingers, localize to the cytoplasm (Molnar et al., 1994, Mol Cell Biol 14: 8292-8303; Sun et al., 1996, EMBO J. 15: 5358-5369). The formation of homo- and heterodimers among the DNA binding isoforms increases their affinity for DNA (Sun et al., 1996, EMBO J. 15: 5358-5369). Aiolos and Helios can dimerize with all Ikaros isoforms via their shared carboxy-terminal zinc finger domains to form stable multimeric complexes, act in concert with Ikaros, and may partially complement its function (Morgan et al., 1997, EMBO J. 16: 2004- 2013; Kelley et al., 1998, Curr Biol. 8: 508-515; Hahm et al., 1998, Gene Dev. 12: 782-796). These different multimeric complexes are thought to control the transcription of developmentally important genes during lymphocyte ontogeny and thereby play pivotal roles for the orderly maturation of lymphocyte precursors

(Brown et al., 1997, Cell 91: 845-854, Kim et al., 1999, Immunity 10: 345-355).

Non-DNA binding Ikaros proteins with fewer than three amino-terminal zinc fingers can act as "dominant-negative" regulators by interfering with the ability of DNA binding Ikaros isoforms to form homo- and heterodimers or complexes with Aiolos and Helios (Sun et al., 1996, EMBO J. 15: 5358-5369). It is therefore conceivable that inappropriate expression of non-DNA binding Ikaros isoforms during early lymphopoiesis may dysregulate normal lymphocyte development. Such a developmental error could lead to a maturational arrest at discrete stages of lymphocyte ontogeny and predispose lymphocyte precursors to leukemic "second hits" and leukemic transformation. This hypothesis is supported by the fact that a deletion of three amino-terminal zinc fingers of Ikaros results in a dominant negative mutation and leads to development of lymphoblastic leukemia in germline mutant mice between the third and six months after birth (Winandy et al., 1995, Cell 83: 289-299). Recent studies have shown that immature lymphocyte precursors express DNA-binding isoforms of Ikaros that localize to centromeric heterochromatin, which may lead to gene silencing (Kim et al., 1999, Immunity 10: 345-355; Brown et al., 1999, Mol Cell 3: 207-217). Thus, Ikaros might play an important role in recruitment and centromere-associated silencing of growth regulatory genes (Kim et al, 1999, Immunity 10: 345-355; Brown et al., 1999, Mol Cell 3: 207-217). An abundance of dominant-negative or mutant Ikaros isoforms that no longer bind DNA would interfere with centromeric recruitment and repression of specific genes during lymphocyte development. Recent studies implicated the expression of dominant- negative Ikaros isoforms and/or the disruption of normal Ikaros function in the leukemogenesis of ALL in infants, children, as well as adults (Sun et al., 1996, EMBO J. 15: 5358-5369, Sun et al, 1999, JClin Oncol 17: 3753-3766; Sun et al., 1999, Clin Cancer Res 5: 2112-2120; Sun et al., 1999, Proc. Natl. Acad. Sci. USA. 96: 680-685; Hosokawa et al., 2000, Blood 95: 2719-2721; Nakase et al., 2000, Cancer Res 60: 4062-5). Aiolos interacts with Ikaros through their shared carboxy-terminal zinc fingers.

Further, both Aiolos and Ikaros were found in the high order chromatin structures and associated with histone deacetylase Mi-2 and SWI/SNF complex (Morgan et al., 1997, EMBOJ. 16: 2004-2013, Koipally et al., 1999, EMBO J. 18: 3090-3100, Kim et al.,

1999, Immunity 10: 345-355). While Ikaros expression is detected at the earliest stages of hematopoiesis preceding lymphoid lineage commitment, Aiolos expression is first detected at low levels in early lymphocyte precursors and its expression level increases as lymphocyte precursors mature to more advanced stages of ontogeny to peak in mature B-lymphocytes. Aiolos plays a critical role in normal B-cell ontogeny since targeted disruption of the Aiolos gene in mice leads to significant abnormalities of the B-lymphocyte compartment, including development of B-cell malignancies

(Wang et al., 1998, Immunity 9: 543-553). The involvement of Ikaros in the development of lymphocytes and other hematopoietic cell types underscores the importance of the expression of this gene, and its related isoforms. There is also the need for other markers of cellular developmental control that may also be useful in the diagnosis of developmental processes and disorders.

Summary

Disclosed herein is the cloning and sequencing of a nucleic acid that encodes Helios 3, a member of the Kruppel family of "zinc finger" DNA-binding proteins. Helios 3 (SEQ ID NO:l) was cloned from a human T-cell leukemia cDNA library and encodes a 304 amino acid protein isoform (SEQ ID NO:2) which lacks four amino terminal zinc fingers, FI - F4, present in the Helios 1 and 2 isoforms. Helios 3 also contains a N-terminal 15 amino acid sequence (SEQ ID NO: 10) that is not common to either Helios 1 or 2 proteins, hi addition, the 5' end of the Helios 3 m NA contains an extensive 5' untranslated region (5' UTR). The present invention also provides probes for the detection of Helios 3.

Such probes include antibodies which can specifically recognize the N-terminus of Helios 3. Additionally, the invention provides nucleic acid probes for the detection of Helios 3 mRNA, which are specific for the 5' untranslated region and the coding region for the 15 amino acid N-terminus. The present invention also provides the association of Helios 3 expression with hematological abnormalities, and in particular, abnormalities associated with the developing immune system. The invention provides for the diagnosis of forms of acute lymphoblastic leukemia (ALL) by determining the expression of Helios 3 in cell samples from patients.

The current invention also provides information allowing for the identification of non-functional Helios isoforms, in particular Helios isoforms that lack, or that contain mutations within, the amino terminal zinc fingers F1-F4. Since non-functional Helios isoforms are predicted to be deficient in protein-protein interactions with other regulators of lymphocyte differentiation, the expression of these non-functional Helios isoforms can be correlated with a cellular abnormality. In particular, the present invention provides for the correlation of the expression of Helios isoforms that contain an N-terminal deletion or mutation with acute lymphoblastic leukemia (ALL). The current invention also provides methods for the detection of Helios isoforms that contain an N-terminal deletion or mutations.

Brief Description of the Drawings Figure 1 shows a schematic diagram of the alignment of three human Helios gene isoforms 1, 2, and 3. Zinc fingers FI, F2, F3, F4, F5 and F6 are indicated by black vertical bars. Probes A-C as used in Southern and Northern blot experiments are indicated by lines underneath the Helios isoforms. The relative location and orientation of oligonucleotides primers PF1, PR1, PF3, and PR3 used in RT-PCR are indicated by arrows.

Figure 2 shows southern blot analysis indicating that human Helios 1, 2 and 3 are encoded by the same gene locus. Three different genomic DNA clones from the human RPCI-1 genomic library were first isolated using the Helios 3 probe, (SEQ ID NO:3) digested with EcoRI and then subjected to Southern blot analysis using three Probes A-C as detailed in Figure 1.

Figure 3 demonstrates the expression of both Helios 1 and Helios 3 in human thymic cells and Jurkat cells using RT-PCR analysis. Location and orientation of the oligonucleotide primers (SEQ ID NOS.6-10) used for RT-PCR are indicated in Figure 1. Figure 4 demonstrates the expression of Helios isoforms in various leukemia cell lines by Northern analysis using probes specific for Helios 1 and Helios 3 as indicated in Figure 1.

Figure 5 demonstrates the expression of Helios 1 and 3 in diagnostic bone marrow specimens from T-lineage and B-lineage ALL patients by RT-PCR analysis.

Figure 6 shows the interaction of Helios 3 with itself, Helios 1, Ikaros 1-4, and Aiolos as determined by the yeast two-hybrid assay. The Bait-Prey grid represents potential protein-protein interactions (Hell=Helios 1, Hel3=Helios 3,

Ikl=Ikaros 1, Ik2=Ikaros 2, Ik3=Ikaros 3, Ik4=Ikaros 4, Aio=Aiolos) and a positive protein-protein interaction is indicated by a dark patch of cells (blue in original).

Detailed Description of the Invention

All scientific and technical terms used in this application have meanings commonly used in the art unless otherwise specified. As used in this application, the following words or phrases have the meanings specified.

As used herein, "Helios isoforms" refer to the products of Helios gene expression that include nucleic acid and protein products that can have variable sizes and sequences. Helios isoforms include Helios 1, Helios 2, and Helios 3 nucleic acids and proteins. Helios isoforms can be produced by alterations in the genomic sequence of Helios, post-transcriptional nucleic acid processing or splicing, or post- translational protein modification or processing. As used herein, 'Helios variants' or 'Helios variations' refer to changes in amino acid or nucleotide sequence of a particular Helios isoform.

As used herein, "specific immunoreactivity" refers to ability of a particular compound to be specifically identified by an antibody through physical interaction.

As used herein, "lymphohematopoietic" refers to cells, components, or processes of the bone and lymphoid system.

As used herein, "lymphoid abnormality" or "lymphoid disease" means a disease involving T-cells or B-cells, and includes malignancies or leukemias, for example, stem cell leukemia, T-cell or B-cell ALL, and secondary leukemia. As used herein, 'Helios C-terminus' or 'C-terminal region' refers to the common region of the Helios proteins located towards the carboxy-terminal end of the Helios protein that contain the F5 and F6 zinc fingers. This region corresponds to amino acids 16-304 of Helios 3 (SEQ ID NO:2) and amino acids 238-526 of Helios 1 (SEQ ID NO:5).

As used herein, "amino-terminal zinc fingers" means the amino acid residues comprising zinc fingers FI, F2, F3, and F4 that are conserved in the amino-terminal region of the Helios 1 and Helios 2 proteins.

As used herein, "dysfunctional Helios isoforms" means a Helios protein that lacks the ability to physically associate with various Ikaros, Aiolos, or Helios isoforms due to mutations in the N-terminus or a deletion of the N-terminus.

The invention is based on the discovery of a novel human Helios isoform (herein referred to as 'Helios 3'), polynucleotides encoding Helios 3, and the use of these compositions for the diagnosis, prevention, or treatment of hematological malignancies and disorders. These compositions are particularly useful in the diagnosis, prevention, or treatment of lymphohematopoietic abnormalities.

Helios 3 isoform

Isolated nucleic acids that encode the Helios 3 protein was first identified from a human T-cell leukemia (JURKAT) 5' stretch cDNA library constructed in λgtl 1. A mouse Helios A/B nucleic acid probe was used to screen the leukemia cDNA library and plaques that positively reacted with the Helios A B nucleic acid probe were purified after two rounds of low stringency hybridization and one round of high stringency hybridization. The cDNAs of positive plaques were subcloned and sequenced, and the nucleic acid sequence of a unique human Helios cDNA clone, Helios 3, (SEQ ID NO:l) was determined.

One embodiment of the invention includes a protein encoded by the Helios 3 cDNA clone. As shown in Table 1, the Helios 3 protein consists of a 304 amino acids sequence (SEQ ID NO:2). As shown in Figure 1, the C-terminal 289 amino acids of Helios 3 protein is identical to the C-terminal sequences of the Helios 1 (SEQ ID NO:5) and Helios 2 proteins which contain two zinc fingers, F5 and F6. The 15 amino acid N-terminus of Helios 3 (SEQ ID NO: 10) is different than the N- terminus of Helios 1, which is approximately 237 amino acids in length (from the corresponding amino acid N16 in Helios 3) and contains four zinc finger motifs, Fl-

F4. The 15 amino acid Ν-terminus of Helios 3 does not contain zinc fingers or display homology to the Ν-terminus of Helios 1. In another embodiment, the invention includes a peptide comprising the 15 amino acid Ν-terminus of Helios 3 (SEQ ID NO: 10) as shown in Table 1.

The invention also includes protein or peptide variants of Helios 3, for example variants of SEQ ID NO:2 or SEQ ID NO: 10 containing amino acid variations. Variants can include proteins having preferably at least 80%, more preferably more than 90%, and most preferably more than 95% amino acid sequence identity to Helios 3 (SEQ ID NO:2) or the peptide corresponding to the 15 amino acid N-terminus of Helios 3 (SEQ ID NO: 10). The Helios 3 variant preferably retains the functional or antigenic properties of the Helios 3 protein (SEQ ID NO:2) or the peptide corresponding to the 15 amino acid N-terminus of Helios 3 (SEQ ID NO:10).

Variants of Helios 3 can include those that contain conserved amino acid substitutions that can be made according to Table 1. According to Table 1 these variants can contain amino acid substitution at a certain residue on condition that the amino acid being replaced is within the same group, as indicated by parenthesis, as the one replacing it.

Aromatic: (His Phe Trp Tyr)

Aliphatic: Non-polar (Gly Ala Pro He Leu Val)

Polar, uncharged (Cys Ser Thr Met) (Asn Gin)

Polar, charged (Asp Glu)

(Lys Arg)

Other (Asn Gin Asp Glu) In another embodiment, the invention includes nucleic acids that encode the

Helios 3 protein or a portion thereof. Nucleic acids that can encode the Helios 3 protein or portion thereof include both polydeoxyribonucleic acid (DNA) and polyribonucleic acid (RNA) molecules. Consequently, this includes any nucleic acid sequence which encodes the Helios 3 protein (SEQ ID NO:2) or any sequence that encodes the 15 amino acid N-terminal portion of Helios 3 (SEQ ID NO: 10) or a protein that contains this N-terminal portion. In a particular embodiment, the invention includes a nucleic acid according to the nucleic acid sequence of (SEQ ID

NO:l), as shown in Table 1. The nucleic acid encoding the Helios 3 protein is 3.5 kb in length and contains a 1300 nucleotide 5' untranslated region (5' UTR), a 912 nucleotide open reading frame (ORF), and a 1346 nucleotide 3' UTR, followed by a polyadenlyation signal. The first 1345 nucleotides of the Helios 3 nucleic acid sequence, which contains the 5' UTR and the first 15 codons of the open reading frame (ORF) is not homologous to the 5' UTR of the Helios 1 (SEQ ID NO:5) or Helios 2 nucleic acids. In another particular embodiment, the invention includes a nucleic acid, or a portion thereof, according to the unique 5' end of the Helios 3 nucleic acid, which consists of 1300 nucleotides of 5' untranslated region (5' UTR) and the first 45 nucleotides of the ORF, encoding the 15 amino acid N-terminus of Helios 3 (nucleotides 1-1345 of SEQ ID NO:2). The invention also encompasses variations in nucleic acid sequences, for example, variations in SEQ ID NO:l, encoding the Helios 3 protein (SEQ ID NO:2) or the N-terminus of the Helios 3 protein (SEQ ID NO: 10) as a result of the degeneracy of the genetic code. These variations can be made by conservative changes in the nucleotide sequence of one or more than one codon of the Helios 3 nucleic acid sequence. Based on this degeneracy, it is understood that a multitude of nucleotide sequences may be realized that encode a protein that is identical to Helios 3 (SEQ ID NO:2). Additionally, the sequence of a nucleic acid that encodes Helios 3 can also be altered when Helios 3, or a portion thereof, is being expressed in a particular expression system wherein the alteration in the Helios 3 nucleic acid sequence is carried out to accommodate codon preference in the expression system. For example, the nucleic acid sequence of a codon can be changed, the codon change being conservative, and which alters the rate at which expression of the Helios 3 occurs in the particular expressions system. Such expression systems can be, for example, prokaryotic or eukaryotic cells transformed with a Helios 3-containing expression construct. The Helios 3 nucleic acid sequence can also be altered to provide a transcript that has certain desired properties, for example, a Helios 3 messenger RNA molecule providing an increased half-life or a desired secondary structure.

The invention also includes nucleic acid sequences that can hybridize to the Helios 3 nucleic acid sequence under various hybridization conditions, or under conditions of varying stringency. These nucleic acids can be useful, for example, as probes for detecting the expression of Helios 3 nucleic acid, if present, in a sample. Hybridization conditions and methods to alter the stringency of hybridization are known in the art and can be found in references, for example, Current Protocols in Molecular Biology (Ed.: Ausubel et al., 1990, Greene Pub. Associates and Wiley- Interscience: John Wiley, New York). Particularly useful nucleic acids of the current invention are ones that hybridize to the 5' end of the Helios 3 nucleic acid, for example, to any of nucleotides 1-1345 of SEQ ID NO:l. These nucleic acids can be DNA or RNA and can be directed to hybridize to either the sense or anti-sense nucleic acid strand of Helios 3 DNA or the to the RNA transcript of Helios 3. Helios 3 nucleic acids used in hybridization to a complimentary Helios 3 nucleic acid are preferably greater than 10 nucleotides in length, more preferably greater than 15 nucleotides in length, and most preferably greater than 20 nucleotides in length. The nucleic acids used in hybridization can also contain nucleotides that form mismatched basepairs with the Helios 3 nucleic acid target or can contain additional nucleotide sequences that are not complimentary with the Helios 3 nucleic acid target. These nucleic acids can be used in various procedures involving hybridization of Helios 3 nucleic acids, for example PCR. These mismatches or additional nucleotide sequences can be used to introduce useful nucleotide sequences, for example, restriction enzyme sites or protein-binding sites. Nucleic acids containing these mismatches or additional nucleotide sequences preferably are able to hybridize to Helios 3 nucleic acids under conditions of increased stringency. Functional significance of the N-terminal zinc fingers Z1-Z4.

The Helios 3 protein (SEQ ID NO:2) lacks four N-terminal zinc finger motifs, F1-F4, found in Helios 1 and Helios 2 proteins. The current invention has addressed the functional significance of these N-terminal zinc fingers, F1-F4, in Helios protein function. The yeast Saccharomyces cerevisiae two-hybrid system (Ruden, D.M., Nature 350:250-252) was utilized to determine the ability of the Helios 3 protein to interact with other transcriptional factors of the Kruppel family of zinc finger DNA-binding proteins involved in controlling lymphocyte development. The proteins include ikaros 1, Ikaros 2, Ikaros 3, Ikaros 4, Aiolos, and Helios 1. Other biochemical techniques, for example, co-immunoprecipitation, or genetic techniques, for example, genetic suppression in the yeast Saccharomyces cerevisiae, can be used to determine the interaction of the Helios 3 protein with other proteins.

As shown in Figure 6, the two-hybrid assay indicated that Helios 3 displays weak or little protein-protein interactions with Ikaros 1, Ikaros 3, Ikaros 4, Aiolos and Helios 1. Helios 3 also was not able to interact with itself, or dimerize. The wild type Helios isoform, Helios 1, however, was able to interact with Ikaros 1, Ikaros 2, Ikaros 3, Ikaros 4, and Aiolos. Helios 1 also was able to interact with itself, or dimerize. Therefore, the present invention provides an understanding of the functional significance of the N-terminal zinc fingers, F1-F4, in mediating critical protein-protein interactions and indicates that absence or mutation of these zinc fingers in other Helios isoforms is likely to result in the same loss of protein functionality, as seen in the Helios 3 protein.

Therefore, another embodiment of the current invention is a method to detect hematological abnormalities, for example, B and T lymphocyte abnormalities, by analyzing a sample for the expression of functionally-deficient isoforms of Helios which result from aberrations in the N-terminus containing the F1-F4 zinc fingers. Aberrations in the N-terminus of Helios containing the F1-F4 zinc fingers can include, but are not limited to, N-terminal truncations, mutations in the F1-F4 zinc finger domains, frameshift mutations in the N-terminal region, mutations of the N- terminus arising due to splicing defects, and improper folding of the N-terminal region so the that F1-F4 zinc finger domains are not functional.

Detection of Helios 3

The current invention also encompasses detection of Helios 3 isoforms, including nucleic acids and amino acids.

One embodiment of the invention includes detecting hematological abnormalities in a sample by assaying for the expression of the Helios 3 protein, using either polyclonal or monoclonal antibodies specific for the Helios 3 protein. These procedures are known in the art and can be found in various references, for example, Current Protocols in Immunology (Ed.: Coligan et al., 1991, John Wiley & Sons, New York, NY). Examples of procedures that can be used to detect the expression of Helios 3 include, but are not limited to, Western blotting, enzyme- linked immunosorbent assay (ELISA), radioimmunoassay (RIA), fluorescence activated cell sorting (FACS), and immunofluorescence microscopy. However, it is understood that a wide variety of antibody-based protein detection methods are available and can be applied for detection of the Helios 3 protein.

One particulary useful embodiment of this invention includes detecting hematological abnormalities in a sample by determining the expression of Helios 3 using antibodies that specifically recognize Helios 3. Specific recognition of Helios 3 can be accomplished by generating probes against the N-terminal amino acid sequence of Helios 3 (SEQ ID NO: 10), a portion of the N-terminal sequence, or other polypeptide sequences that contain this N-terminal sequence.

In one embodiment, the probe can be an antibody, for example, a monoclonal or polyclonal antibody, directed against the N-terminal amino acid sequence of Helios 3 (SEQ ID NO: 10), a portion of the N-terminal sequence, or other polypeptide sequences that contain this N-terminal sequence. The Helios 3 peptide or protein can be produced and optionally purified to enable the production of an antibody against Helios 3. The Helios 3 peptide, for example SEQ ID NO: 10, or a portion of this sequence, can be used as an immunogen in production of the antibody. The Helios 3 peptide can be produced by a variety of methods including solid phase chemical synthesis, for example Fmoc chemistry. Peptide synthesizers, for example, the Peptide Synthesis System 433 A (Applied Biosystems, Foster City,

CA) and methods for using them are commonly known in the art. Alternatively,

Helios 3 peptides may be commercially synthesized by various companies, for example, by Research Genetics (Huntsville, AL 35801). Proteins or peptides containing the N-terminal amino acid sequence of Helios

3 (SEQ ID NO: 10), a portion of the N-terminal sequence, or other polypeptides that contain this N-terminal sequence can be produced by employing molecular biology techniques. For example, a nucleic acid encoding the desired Helios 3 protein or peptide can be inserted into a vector or plasmid for expression and production of Helios 3-containing proteins in either prokaryotic or eukaryotic expression systems. A nucleic acid sequence encoding the desired Helios 3 protein or peptide can be inserted into an expression vector enabling the production of a Helios 3 protein containing SEQ ID NO:2, SEQ ID NO:10 or a portion of SEQ ID NO:10. Nucleic acids can also be constructed that allow the expression of the Helios 3 protein, or a portion thereof, fused other amino acid sequences useful in the production and purification of Helios 3. For example, additional amino acid sequences can be useful in the purification of Helios 3, or a portion thereof. Additional amino acid sequences, or "tags", for example, multiple histidine residues, FLAG, or hemagluttinin (HA) sequences can be fused to the Helios 3-containing amino acid sequence. Methods for purifying fusion proteins containing these tags, for example, nickel-resin chromatography or FLAG or HA-immunoaffmity chromatography can be used to purify the Helios 3-containing protein and are commonly known in the art. Protein cleavage sequences, for example, the enteropeptidase recognition site, can also be fused to the Helios 3-containing protein and can be useful in the purification process. Vectors enabling the production of Helios 3-containing proteins, for example, the pRSET vector (Invitrogen, San Diego, CA) and expression systems, for example E. coli BL21 (Invitrogen, San Diego, CA) can be obtained commercially. Methods for the synthesis and production of peptides or polypeptides containing a desired sequence are commonly known in the art and can be found in references, for example, Current Protocols in Protein Science (Ed.:

Coligan et al., 1996, John Wiley & Sons, New York, NY). Optionally, the Helios 3 peptide can be purified following synthesis. Purification can be achieved by a variety of methods, for example, by gel filtration, or acrylamide or agarose gel electrophoresis.

In addition to Helios 3-containing peptides or proteins for generating antibodies against Helios 3, this invention also includes Helios 3 recombinant proteins, nucleic acids used to encode these proteins, and expression systems, for example prokaryotic and eukaryotic organisms transformed with the Helios 3- expressing nucleic acids.

Methods for the production of antibodies displaying immuno-specificity against the N-terminal amino acid sequence of Helios 3 (SEQ ID NO: 10), a portion of the N-terminal sequence, or other polypeptides that contain this N-terminal sequence can be employed upon the production and purification of the peptide or a polypeptide containing the Helios 3 sequence. Preferably, a contiguous sequence of at least eight amino acids of SEQ ID NO: 10 is used as an immunogen for antibody production, more preferably the sequence is at least eleven amino acids, and most preferably the sequence is fifteen amino acids in length. Production of monoclonal antibodies can be accomplished in mammals, for example, in mice, by the administration of the Helios 3 peptide or protein to a mouse (immunization), isolation of a population of B cells from the spleen, fusion of the B cell clones with immortalized cells, for example, myeloma cells to create a hybridoma clones, and subsequent screening of the hybridoma clones that produce the monoclonal antibody with specific immunoreactivity against the Helios 3 peptide or protein used in immunization. Hybridomas can be propagated in mice and the monoclonal antibody can be collected from ascites fluid. Alternatively, hybridomas can be grown in appropriate media and the antibody can be collected from the supernatant. Production of polyclonal antisera can be accomplished in mammals, for example, in rabbits, by administration of the Helios 3 protein or peptide to rabbits (immunization) and the subsequent collection of rabbit sera, after a period of time, containing antibodies against the Helios 3 peptide or protein used in immunization. Antibodies, either monoclonal or polyclonal, can be subsequently purified using affinity chromatography techniques, for example, Protein A-Sepharose or anti-mono or polyclonal antibody immunoaffinity chromatography. Techniques and variations in techniques for the production of monoclonal and polyclonal antibody preparations with immunoreactivity against desired peptides or proteins are commonly known in the art and can be found in various references, for example Current Protocols in

Immunology (Ed.: Coligan et al., 1991, John Wiley & Sons, New York, NY).

Alternatively, polyclonal antisera directed against the Helios 3 peptide or protein can be generated commercially by various companies, for example, by Research

Genetics (Huntsville, AL 35801).

Detection of Helios 3 or other Helios isoforms can be performed by a variety of antibody-based methods, otherwise known as immunodetection. Helios isoform or isoforms, for example, Helios 3, can be detected by western blotting. Proteins samples prepared from cellular lysates can be separated by polyacrylamide gel electrophoresis and transferred to a solid support, for example, a nitrocellulose or a PVDF membrane, by electroblotting. Detection of the immobilized Helios isoform can be accomplished by incubating the membrane in the presence of the anti-Helios antibody followed by incubation with a secondary compound, for example, an antibody or a protein, for example, Protein A/G, which specifically recognizes the anti-Helios antibody. The secondary compound can be coupled to a detection compound, for example, a peroxidase or an alkaline phosphatase molecule, and used with reagents for colorometric or luminescent detection. Compounds, for example, fluorophores or biotin, can also be coupled to the antibody through covalent bonding. Activated derivates of fluorophores or biotin, for example NHS-FITC or NHS-biotin can be reacted with the antibody in the appropriate conditions to provide a labeled antibody. Kits and instructions for these coupling reactions can be obtained commercially from, for example, CALBIOCHEM (San Diego, CA). Blots may be visualized by a variety of methods, for example, X-ray film or detection screens and the relative amount of signal from detection of the Helios isoform can be quantified by, for example, densitometry. Other antibody-based techniques can be used for the detection of Helios isoforms from cellular lysates, for example, dot blots, colony/plaque lifts, enzyme-linked immunosorbent assays (ELISA), and immunoprecipitation. Alternatively, antibody-based techniques can also be used to determine expression of a Helios isoform, in particular Helios 3, from intact but permeabilized cells or tissue. For example, cells or tissues may be fixed with an aldehyde-based reagent, for example, formaldehyde or glutaraldehyde, and permeablized with a reagent, for example, methanol or saponin. Cells or tissues can be then stained with an anti-Helios 3 antibody and then subsequently stained with a secondary detection reagent. The secondary compound can be coupled to a detection compound, as indicated above, or, optionally, a molecule, for example, a fluorphore, such as FITC or Cy3. In another variation in Helios detection, cells can be stained with a nucleic acid probe specific for Helios 3. This nucleic acid probe may be modified, for example, by coupling the nucleic acid to a fluorophore or a molecule that will allow subsequent detection of the nucleic acid by various techniques, for example, by microscopy or flow cytometry. In another example, cells that have been stained with a Helios probe coupled to a fluorophore can be examined by flow cytometry.

Detection of Helios isoforms, such as Helios 3, can be performed employing nucleic acids as probes and utilizing techniques to detect probes in a sample, for example, Northern blotting, reverse transcription-polymerase chain reaction (RT- PCR), RNase protection assay (RPA), or primer extension analysis. The nucleic acid probe can be a single stranded DNA or an RNA oligonucleotide probe which can specifically hybridize to, at least a portion of the nucleic acid sequence encoding the N-terminus of Helios 3 or the 5' UTR of Helios 3 nucleic acid. These nucleic acid probes can be prepared by a variety of methods, for example, solid state nucleic acid synthesis. Commercial nucleic acid synthesizers, for example, the 3948

Nucleic Acid Synthesis and Purification System (Applied Biosystems, Foster City, CA), and methods for utilizing them are available. Alternatively, DNA or RNA containing the Helios 3 sequence of interest can be obtained commercially, for example, from Life Technologies (Rockville, MD). In another example, Helios 3 nucleic acid probes can be prepared by employing molecular biology techniques, for example, in vitro run-off transcription. Techniques for generating single stranded nucleic acid probes can be found in various technical references, for example, Current Protocols in Molecular Biology (Ed.: Ausubel et al, 1990, Greene Pub. Associates and Wiley-Interscience: John Wiley, New York). Nucleic acid probes can be synthesized with modified nucleotides, fluorphore-coupled nucleotides, or other modified nucleotides, for example, 5-(3-aminoallyl)uridine 5'-triphosphate (Sigma, St. Louis, MO) in order to enable detection of the probes. Following synthesis, nucleic acids can be labeled in various ways, for example, by 5 ' or 3' end- labeling with radioactive or fluorescence-coupled nucleotides with enzymes, for example, polynucleotide kinase or terminal transferase. The nucleic acid probe can optionally be purified by, for example, gel filtration or purification, spin columns, or selective precipitation.

Another embodiment of this invention includes detection of functionally deficient Helios isoforms in which a portion, or all, of the N-terminus containing the F1-F4 zinc fingers is absent. Expression of these N-terminal deficient Helios isoforms can be detectable as Helios protein species that are smaller in size as compared to Helios 1. Various immunodetection methods can be used to determine the presence of N-terminal deficient Helios isoforms in a cell sample, for example, by Western blotting. One particularly useful immunodetection method involves using an antibody that specifically recognizes an epitope of the conserved C-terminal region of Helios proteins. Preferably, the antibody can recognize Helios isoforms which display a common epitope on the C-terminus. For example, a useful antibody for detection of Helios 3 would be one that specifically recognizes an epitope or epitopes found within amino acids 16-304 of SEQ ID NO:2. Monoclonal or polyclonal antibodies can be prepared or can be obtained from a commercial source that are specific for the C-terminus of Helios 3. For example, a goat polyclonal antibody directed against an epitope near the common carboxy-terminus of Helios and reactive against mouse, rat, and human Helios is commercially available and can be used to detect Helios isoforms in various assays (cat.# SC-9866, Santa Cruz Biotechnology, Inc., Santa Cruz, CA). Antibodies that recognize the common C- terminus of Helios can be used for the detection of Helios isoforms that have a wild type C-terminus, for example, Helios 1 and Helios 3. Helios isoforms having common C-termini but having different N-termini can be differentiated by their molecular weights using various techniques, for example, Western blotting. These detection methods can also be used to quantify the relative amount of the Helios isoform in a sample. The quantification of particular Helios isoforms in a sample, for example, the quantity of functionally-deficient Helios isoforms to the relative of functional Helios isoforms, can be correlated with the presence of a hematological abnormality in a cell sample. Nucleic acids, in particular RNA, can be extracted from cells or tissues suspected of expressing Helios isoforms. RNA can be separated on agarose or acrylamide gels and then transferred to solid supports, for example, -nitrocellulose or

PDVF membranes. Nucleic acid probes, as described previously, can be used detect Helios mRNA on membranes using various techniques, for example, Northern analysis. Other types of nucleic acid analysis can also be performed, for example,

RT-PCR, by transcribing the Helios RNA into cDNA and performing PCR using downstream oligonucleotides primers and oligonucleotide primers specific for the unique 5' region of Helios 3, complimentary to either the 5' UTR or the region encoding the N-terminus. PCR products can be optionally separated by gel electrophoresis and quantified, for example, by densitometry or fluorescence. Other nucleic acid detection techniques, for example, RNase Protection Assay (RPA) may be performed, by utilizing an antisense RNA probe to 5' region of Helios 3, complimentary to either the 5' UTR or the region encoding the N-terminus. Another embodiment of this invention includes detection of Helios nucleic acid isoforms encoding functionally deficient Helios isoforms in which a portion, or all, of the N-terminus containing the F1-F4 zinc fingers is absent. Nucleic acid probes specific for the 3' portion of Helios RNA, or the 3' portion of a DNA sample that represents Helios RNA, can be used to probe for Helios isoforms in a sample. Preferably, these Helios nucleic acid probes can recognize a 3' Helios nucleic acid portion that codes for a common C-terminal region. These nucleic acid probes can be used to detect the presence of nucleic acids encoding N-terminal deficient Helios isoforms in a sample and distinguish them from wild type Helios nucleic acid isoforms. Preferably, the isoforms will be able to be distinguished by size, wherein the shorter isoforms correspond to Helios nucleic acid isoforms that encode N- terminally deficient Helios proteins. Various methods can be used to determine the presence of these isoforms, for example, Northern blotting or primer extension.

Samples containing Helios isoforms

The presence of Helios 3 or Helios isoforms can be analyzed in a variety of cell types from a patient or a group of patients displaying a common disease. Cell samples can be obtained by extracting the cells ex vivo from the patient. Cell samples can be obtained from tissue samples, for example, from biopsies, or from peripheral blood or preparations of peripheral blood, for example, from an enriched fraction of the blood. Cell samples can also be obtained from the bone marrow, for example, by aspiration. Preferably, Helios 3 expression is examined in cell samples obtained from the bone marrow in patients having or suspected of having a hematologic abnormality.

Cell samples, when obtained, can be processed or treated in a variety of ways to examine the expression of Helios 3. Cell extracts can be prepared by the lysis or solubilization of cells in detergents, optionally using methods, for example, sonication or homogemzation, to release cellular constituents, in particular, proteins. Ionic or non-ionic detergents can be used, for example, sodium dodecyl sulphate (SDS), Triton X-100, sodium deoxycholate or CHAPS. Cells may also be disrupted in the presence of chaotropic reagents, for example, urea or guanidine salts. Other reagents can be added to the detergent or chaotropic reagent, for example, a buffer, such as Tris or HEPES, salts, for example KC1 or NaCl, or other reagents which stablilize the constituents of the cell lysate, for example, protease inhibitors, such as PMSF, pepstatin, or EDTA. However, a variety of methods and buffer compositions are available for the lysis or disruption of cells for protein extraction which are commonly known in the art and can be found in references, for example, Current Protocols in Protein Science (Ed.: Coligan et al., 1996, John Wiley & Sons, New York, NY). Cells can also be lysed or solubilized in detergents or chaotropic reagents in order to release and purify nucleic acids, in particular RNA. Other reagents may be added to the detergent or chaotropic reagent, for example, a buffer, such as Tris or HEPES, salts, for example KC1 or NaCl, or other reagents which stablilize the nucleic acid in the sample, for example, nuclease inhibitors, such as RNasin (Promega, Madison, WI), diethypyrocabonate (DEPC),'or EDTA. Extraction of nucleic acids can also be accomplished using phenol: chloroform extraction. Other methods for the isolation of nucleic acids, for example, RNA and in particular messenger RNA can be used. These include, for example, spin columns and oligo dT-based purification reagents. A variety of kits can be commercially obtained for the purification of nucleic acids, in particular RNA, from, for example, Ambion, Inc. (Austin, TX 78744). However, a variety of methods and buffer compositions are available for the lysis or disruption of cells for nucleic acid extraction which are commonly known in the art and can be found in references, for example, Current Protocols in Molecular Biology (Ed.: Ausubel et al, 1990, Greene

Pub. Associates and Wiley-Interscience: John Wiley, New York).

EXAMPLE 1 Molecular cloning and characterization of Helios 3.

The present application involves steps aimed to characterize the mRNA species encoded by the human Helios gene in leukemic cells. As a first step to clone the cDNA for human Helios, RT-PCR (reverse transcription - polymerase chain reaction) was performed using mRNA isolated from mouse thymocytes as a template and primers specific for mouse Helios. The resulting PCR product containing the full length mouse Helios A/B and the 1.2 Kb C-terminal EcoR I-Sal I fragment of this cDNA clone were labeled with ³²P-dCTP using DECAprime II

DNA labeling kit (Ambion Inc., TX) according to instructions provided with the kit.

The mouse Helios probes were used in the screening of a human T-cell leukemia (JURKAT) 5' stretch cDNA library constructed in λgtl 1 (CLONTECH, CA). 4xl0⁶ independent phage plaques were screened and three rounds of hybridization were performed to purify the positive plaques. The hybridization was carried out at 65°C with 2x10⁶ cpm /ml of the cDNA probe for 2 hours in Rapidhyb solution (Amersham). At least three washes from low stringency (2XSSC/0.1%SDS) to high stringency (0.1XSSC/0.1%SDS) were performed after hybridization. Helios cDNAs contained in the purified phage clones were subcloned into pBluescript vector (Stratagene) and sequenced with Thermosequenase Kit and ALF automated sequencer (Amersham Pharmacia), as previously described (Sun et al., 1999, Proc. Natl. Acad. Sci. USA. 96: 680-685). A number of overlapping clones were isolated and found to contain the same 3' region. A 3.5 kb human Helios cDNA clone (SEQ ID NO:l) was sequenced at least twice to ensure the accuracy of the sequences. The sequence of this cDNA clone (SEQ ID NO: 1) was then analyzed with

Strider program (Macintosh) and was found to contain a 912 bp open reading frame

(ORF) encoding a novel 304 amino acid (AA) peptide (SEQ ID NO:2), which was designated as Helios 3. The polyadenylation signal was found 1346 bp downstream of the stop codon and the 3' untranslated region is homologous to that of mouse

Helios cDNA. The amino acid sequence of the novel Helios peptide was compared to the sequence of the previously cloned human Helios 1 and 2 isoforms using the

PILEUP computer program (GCG, Wisconsin Package). The sequence of the 289

AA C-terminal portion of Helios 3 downstream of amino acid V16 is identical to the corresponding sequence found in Helios 1 (SEQ ID NO:5) and Helios 2 and contains two zinc fingers. By contrast, the 15 amino acid amino-terminal portion of Helios 3 (SEQ ID NO: 10) is unique and does not contain the amino-terminal zinc fmger motifs that are conserved in Helios 1 and 2 as well as other previously identified members of the Ikaros gene family (Figure 2). A BLAST homology search for this 15 amino acid peptide in the GenBank protein data base revealed no similarity to any deposited sequence.

Next, genomic DNA fragments of the human Helios gene locus were cloned in order to determine whether Helios 3 is encoded by the same genomic locus as Helios 1 and Helios 2. Genomic clones of the human Helios gene locus were obtained by screening a Bac Human RPCI-1 genomic library (Genomsystem Inc.) using the 3.5 kb cDNA fragment that contains full length human Helios 3 as the probe (SEQ ID NO:l). 10 μg of DNA from each genomic clone was digested with EcoRI, separated by agarose gel electrophoresis, transferred to nylon membranes (MAGNA, MA) and cross-linked by UV light exposure. These blots were subjected to comparative Southern blot hybridization analyses using probes specific for amino- terminal portions of Helios 1 and Helios 2 cDNA (=Probe A), the 5' UTR of Helios 3 cDNA (=Probe B) and shared carboxy-terminal portion of Helios 1, 2 and 3 cDNAs (=Probe C). Southern blot membranes were first prehybridized in Rapidhyb buffer (Amersham, IL) at 65 °C for 1 hour and then hybridized with the radioactively labeled probe (lxlO⁶ cpm/ml) in Rapidhyb buffer at 65 °C for 1.5 hour with shaking. Northern blot membranes were pre-hybridized in ULTRA-hyb (Ambion Inc., TX) solution for 4 hours and then hybridized with the radioactive labeled probe (lxl 0⁶ cpm/ml) in ULTRA-hyb solution at 42 °C over night. Southern and Northern blot membranes were washed at least three times after hybridization with low and high stringency and exposed to X-ray film. As shown in Figure 2, Probe C hybridized to a 4.1 kb genomic DNA fragment from all three clones. Similarly, Probe B hybridized to a 8.0 kb genomic DNA fragment from all three clones. By comparison, Probe A hybridized to a faint 4.2 kb band from all three clones as well as two fragments of 3 kb and 5 kb size from clone #1 which contains more of the 5' genomic sequence of the Helios locus than clone #2 or clone #3. These results indicate that all Helios cDNAs are encoded by the same genomic locus and Helios 1, Helios 2 and Helios 3 are distinct isoforms generated by alternative pre-mRNA splicing.

EXAMPLE 2 Expression of Helios 3 in human leukemia cells

The expression pattern of Helios 3 was determined in leukemic cell lines MOLT-3/T-lineage ALL, Jurkat/T-lineage ALL, HL-60/AML, ALL-l/t9;22 B- lineage ALL, NALM-6/B-lineage ALL, RS4;ll/B-lineage ALL which were obtained from the Cell Biology Laboratory of the Parker Hughes Institute. Helios 3 expression patterns were also determined in highly leukemic cell-emiched-Ficoll- Hypaque-separated bone marrow mononuclear cells from 15 children with newly diagnosed high risk ALL. Diagnostic bone marrow aspirate samples were obtained with informed consent from parents, patients or both according to Department of Health and Human Services guidelines as part of the CCG-1961 frontline chemotherapy program for newly diagnosed high risk ALL. This research was approved by the Parker Hughes Institute IRB.

Total RNA was isolated from cell lines and freshly obtained leukemic cells from children with newly diagnosed high risk ALL using the ULTRASPEC RNA isolation system (BioTECX). Briefly, 5xl0⁷ cells were homogenized in 5 ml

ULTRASPEC solution and incubated on ice for 5 minutes. 1 ml of chloroform was added and the mixture was vortexed for 25 seconds and incubated on ice for 5 minutes. After centrifugation at 10,000 rpm for 15 minutes, the supernatants were transferred to new tubes and the total RNA was precipitated by adding 6 ml isopropanol. The RNA pellets were washed with 75% cold ethanol and air dried.

The final total RNA was dissolved in DEPC treated water. mRNA was then further purified from total RNA using a mRNA isolation kit (Boehringer Mannheim) according to manufacturers' instructions. The total RNA was diluted in lysis buffer and incubated at 65 °C for 2 minutes. 3 μl biotin labeled oligo (dT) was added to the mixture and incubated for 5 minutes at 37 °C. 300 μl pre- washed streptavidin magnetic beads were then added and incubated at 37 °C for 5 minutes. The beads were washed three times with washing buffer and the bound mRNA was eluted by adding 50 μl DEPC treated water and incubation at 65 °C for 2 minutes. mRNA was used in all RT-PCR experiments as previously described. Pooled mRNA from human thymus and bone marrow was obtained (CLONTECH). The location of primers used are indicated in Figure 2. The sequences of primers are listed in Table 1 where PF1 = SEQ ID NO:6; PR1 = SEQ ID NO:7; PF3 = SEQ ID NO:8; PR3, = SEQ ID NO:9.

Helios 3 was cloned from a cDNA library derived from JURKAT/T-ALL leukemia cells. The expression of Helios 3 mRNA was examined by RT-PCR in JURKAT cells as well as normal thymocytes . As shown in Figure 3, Helios 3 mRNA was detected in JURKAT leukemia cells as well as normal thymocytes. In both cell types, Helios 3 mRNA expression was less than Helios 1 mRNA expression. Notably, JURKAT cells appeared to express higher levels of Helios 1 and Helios 3 mRNA as compared to normal thymocytes.

Northern blot analyses was then used to determine Helios 1 and Helios 3 mRNA in various leukemic cell lines. RNA was prepared from immortalized human leukemia cell lines MOLT-3/T-ALL, JURKAT/T-ALL, RS4;ll/t4;ll pro-B ALL, ALL-l/t9;22 pre-pre-B ALL, NALM-6/pre-B ALL, HL-60/AML, denatured, separated by gel electrophoresis and transferred to a nitrocellulose membrane. ³²P- labeled DNA probes were then used to detect Helios 1 and Helios 3 mRNA expression. DNA probe A specifically hybridizes to Helios 1/2 and DNA probe B specifically hybridizes to Helios 3. A β-actin specific DNA probe was also used to confirm the RNA integrity of the samples. Figure 4 demonstrates that an 11 kb Helios 1 transcript was present in all leukemia cell lines examined. Similarly, a 13 kb Helios 3 transcript was present in all cell lines but its expression level was significantly lower than the expression level for Helios 1/2. Helios 3 mRNA expression was the highest in the B-lineage ALL cell lines NALM-6 and RS4;11 while the T-lineage ALL cell lines MOLT-3 and JURKAT expressed slightly less

Helios 3 mRNA. Thus, expression of Helios 1 and Helios 3 mRNA is not restricted to T-lineage ALL cells or another immunophenotypically distinct subset of leukemic cells, among the lines tested.

Helios mRNA isoform expression was also determined in primary ALL cells in diagnostic bone marrow specimens from leukemia patients. RT-PCR analysis was performed to examine Helios 1/2 and Helios 3 mRNA expression from bone marrow blasts freshly obtained from 6 children with T-lineage ALL and 9 children with B-lineage ALL in comparison with normal bone marrow mononuclear cells and normal thymocytes. β-actin specific primers were used to determine the expression of β-actin mRNA as a normalizing control in all patient cells and in normal thymus and bone marrow. As shown in Figure 5, cells from 4 of the 6 T-lineage ALL cases and cells from 7 of the 9 B-lineage ALL cases as well as normal thymocytes expressed Helios 1/2 mRNA detectable by RT-PCR. Very low levels of Helios 1/2 mRNA were detected in cells from the remaining ALL cases and normal bone marrow mononuclear cells. By comparison, expression of Helios 3 mRNA was detected in normal thymocytes only in 3 out of 10 T-lineage ALL and 4 out of 9 B- lineage ALL cases and not in normal bone marrow cells. While cells from none of the Helios 1/2 negative cases expressed Helios 3, cells from 5 Helios 1/2 positive cases, including one T-lineage ALL case and 4 B-lineage ALL cases, were Helios 3 negative. Therefore, Helios 3 mRNA was expressed in B-lineage ALL cells, T- lineage ALL cells, as well as AML cells, but not in normal bone marrow mononuclear cells. EXAMPLE 3

Functional Significance the N-terminus of Helios 3

A yeast two hybrid system was used to determine the interaction between Helios 1, 3 and different Ikaros isoforms. cDNAs encoding full length Helios 1, 3, Aiolos and various Ikaros isoforms were cloned in frame to the LexA DNA binding domain in the 'bait' vector pL202 using standard techniques (Zervos et al., 1993, Cell 72: 223-232; Ruden et al., 1991, Nature 350: 250-252). These cDNAs were also cloned in frame to the transcription activation domain B42 in the 'prey' vector p JG4- 5 ( Zervos et al., 1993, Cell 72: 223-232). Combinations of 'bait' and 'prey' vectors were transformed into the EGY48 yeast strain (MATa trpl ura3 his3 LEU2::pLexAop6-LEU2 ) which expresses a functional LEU2 gene and harbors the pJK103 plasmid expressing the lacZ gene under the control of two high affinity ColEl LexA operators in addition to a URA3 gene for plasmid maintainance when the cells are grown on selective media. The interaction between various 'bait-prey' pairs containing different combinations of Helios and Ikaros isoforms were studied by growing the recombinant yeast strains on Ura- His- Trp- Leu- -galactose agar plates and by their ability to develop blue color colonies on Ura- His- Trp- -X-gal- galactose plates due to the activation of the reporter gene (β-galactosidase) expression. Naked 'bait' vector pL202 without insert was used in the negative control pairs.

As shown in Figure 6, Helios 1 is capable of homodimerizing as well as interacting with Ikaros 1, 2, 3, and 4 and also Aiolos. The interaction between Helios 1 and Ikaros 1 was as strong as the interaction between Aiolos and Ikaros 1 or self-interaction of Ikaros 1. By comparison, the interaction of Helios 3 with Ikaros 1, Ikaros 3, Helios 1, and Aiolos was much weaker. Helios 3 strongly interacted with Ikaros 2 but had a moderate interaction with Ikaros 4. Similarly, the ability of Helios 3 to homodimerize was substantially impaired in comparison to the ability of Helios 1 to homodimerize. This data indicates that the carboxy-terminal zinc fingers of Helios isoforms are not sufficient for optimal heterodimerization with other members of the ikaros family, except for Ikaros 2. Thus, the amino-terminal domains of Helios 1 can be involved in protein-protein interactions as well as DNA binding. Alternatively, the unique amino-terminal portion of Helios 3 can reduce the ability of this protein to interact with other proteins via its carboxy-terminal zinc finger domains.

Table 1

SEQ SEQUENCE

ID

NO:

AGACAGGAAAGTTTAGAGTTTTCTGGGTAGGACTTTGGTGGTTTAAAAATGGTATAAGTA ACTTTATTCTTGAAAGAAGAATGTGTTTCAAACTGTAAACCAATTTTTTGTTCTTCAGAG ATCATGGAACACAAACACATTGTTATTTTCAGTGATAACTCCTAAGAGGAGCTGAGTTGT TGTGGGTTCTATGTTTACTTCCCCTATGGAATTTATAATTCAGTATGTTTTACACTGTAC CATATAGCAAAACTTTTAAACTACAGGTAGTTAAGGGCCACCTACAATACATCTGAGGTC CTGTGATCTTATTTTTCTAAACGTAAGCACTGTTTTTCCATAGTTTTGATGCACTGGAGA TTTTATAGACACCCTGGCAGTCCTTACTTTTAACCCTTTAAGGGAATAGTATTTTTCACG GCAGTTTTCGGCAATAACATATGGTCTAAGAGTGGATAAAAGGCAGTCAATAATTTCTGG GAGGGACTTCTACTTTCATAAATTTGTTTGAGAGGTTTTCTTTTAAAGTTGTAATGTGAT GGCAGCATAGTATATGTATTTGTTTCTAAAAGTATGCTTACGATTGTCACTTTATCAGCA TTTAATCAGTGTTAACCAGTCAGCAGAAAAATATAATTATGCTAACAGTAGGGGAGAAAA CCCACTTAGAAATCCCTTTTCTGGTATTTCTCTTTTCACTAGTTTTTTTCAAGATGTGAC CTCCCGGTGTTCTGTCCATAGTTCATTCATCCTTTACTCTTCGAGTAGAAGGTCTTAAAA GTCTTCCTGTCGGCTGTTTCTTTCAAAATCTCCTCAGAGCAATTGCTAATTTGACCTGAA TCTGGTAACTTGGACCCTGTAAGGTTACAGAACTAGGGCTATTTATTTTAGCATTTCTTC AGTAGTATTTACTACTCTTGTTGCAAAGAAAAGGGAATGGGACTTCTTTGTAACCTGTAC CTTGGGTCGAC LKK SDCIFLWFCIVPPMEDCKEQEPIMDNNISLVPFERPAVIEKL

TGNMGKRKSSTPQKFVGEK MRFSYPDIHFDMNLTYEKEAE MQSHM DQAINNAITYLG

AEALHPLMQHPPSTIAEVAPVISΞAYSQVYHPNRIERPISRETADSHENNMDGPISLIRP

KΞRPQEREASPNNSCLDSTDSESSHDDHQSYQGHPALNPKRKQSPAYMKEDVKA DTTKA

PKGSLKDIYKVFNGEGEQIRAFKCEHCRV F DHVMYTIH GCHGYRDP ECNICGYRSQ

DRYEFSSHIVRGVHTFH*

AGGAACACCC GCTGACAAAT GTCTTTCTTT CTTTCTTTCT TTCTCCGTTT CTCTTCAGCC

CGACATTGTC ACCTCCTCCT TGAGGGGTTA GAAGAAGCTG GGAGCTCCCG ACAGAGCTGG

AAATGGTGAT GACTGTTTTT TAATCAGAGG ACAATTTCTT TTCACTGCAC TTTGACTATG

GAAACAGACG CAATTGATGG CTATATAACA TGTGACAATG AGCTTTCACC CGAAGGGGAA

CACGCCAATA TGGCCATTGA CCTCACCTCA AGCACACCCA ATGGACAGCA CGCCTCGCCA

AGTCACATGA CAAGCACAAA TTCTGTAAAG CTGGAAATGC AGAGTGATGA AGAGTGTGAC

AGGCAGCCCC TGAGCCGTGA GGATGAGATC AGGGGCCACG ATGAGGGGAG CAGCCTAGAA

GAACCCCTAA TTGAGAGCAG CGAGGTGGCC GACAACAGGA AAGTCCAGGA CCTTCAAGGC

GAGGGAGGAA TCCGGCTTCC GAATGGTAAA CTGAAATGTG ACGTCTGTGG CATGGTTTGC ATTGGGCCCA ATGTGCTTAT GGTACATAAA AGGAGTCAC CTGGTGAGCG GCCCTTCCAC TGTAACCAGT GCGGAGCTTC TTTTACCCAG AAGGGCAACC TTCTGAGACA CATAAAGTTA

TGTAACCAGT GCGGAGCTTC TTTTACCCAG AAGGGCAACC TTCTGAGACA CATAAAGTTA

CACTCTGGAG AGAAGCCCTT CAAATGTCCT TTCTGTAGCT ATGCTTGTAG AAGAAGGGAC

GCTCTCACAG GACACCTCAG GACCCATTCT GTGGGTAAAC CTCACAAGTG TAACTACTGT

GGCCGAAGCT ACAAGCAGCG CAGCTCACTG GAGGAACACA AGGAACGCTG TCACAACTAT

CTCCAGAATG TCAGCATGGA GGCTGCCGGG CAGGTCATGA GTCACCATGT ACCGCCTATG

GAAGATTGTA AGGAACAAGA GCCTATCATG GACAACAATA TTTCTCTGGT GCCTTTTGAG

AGACCTGCTG TCATAGAGAA GCTCACGGCA AATATGGGAA AGCGCAAAAG CTCCACTCCT

CAGAAGTTTG TGGGGGAAAA GCTTATGCGA TTCAGCTACC CAGATATTCA TTTTGATATG

AACTTAACAT ATGAGAAGGA GGCTGAGCTG ATGCAGTCTC ATATGATGGA CCAAGCCATC

AACAATGCAA TCACCTACCT TGGAGCTGAG GCCCTTCACC CTCTGATGCA GCATGCACCA

AGCACAATCG CTGAGGTGGC CCCAGTTATA AGCTCAGCTT ATTCTCAGGT CTATCATCCA

AACAGGATAG AAAGACCCAT TAGCAGGGAA ACATCTGATA GTCACGAAAA CAACATGGAT

GGCCCCACTT CTCTCATCAG ACCAAAGAGT CGAC SEQ SEQUENCE

ID

NO:

4. GGGCTTGGCT TGGAGGGGGC AAGGGAGGGA AAGAGAGAAG GGGGAAACAC AAAAAACTTC

TTTCTTTCCC CCTCCGTTTA TCTTCAGCCC GACATTGTCA CCTCCTCTTT GAGGGGTTAG

AAGAAGCTGA GATCTCCCGA CAGAGCTGGA AATGCATTGC ACTTTGACTA TGGAAACAGA

CGCTATTGAT GGCTATATAA CGTGTGACAA TGAGCTTTCA CCCGAAAGGG AGCACTCCAA

TATGGCAATT GACCTCACCT CAAGCACACC CAATGGACAG CATGCCTCAC CAAGTCACAT

GACAAGCACA AATTCAGTAA AGCTAGAAAT GCAGAGTGAT GAAGAGTGTG ACAGGAAACC

CCTGAGCCGT GAAAATGAGA TCAGGGGCCA TGATGAGGGT AGCAGCCTAG AAGAACCCCT

AATTGAGAGC AGCGAGGTGG CTGACAACAG GAAAGTCCAG GAGCTTCAAG GCGAGGGAGG

AATCCGGCTT CCGAATGGTA AACTGAAATG TGACGTCTGT GGCATGGTTT GCATTGGGCC

CAATGTGCTT ATGGTACATA AAAGGAGTCA CACTGGTGAA CGCCCCTTCC ACTGTAACCA

GTGTGGAGCT TCTTTTACTC AGAAGGGCAA CCTTCTGAGA CACATAAAGT TACACTCTGG

AGAGAAGCCG TTCAAATGTC CTTTCTGTAG CTACGCCTGT AGAAGAAGGG ACGCCCTCAC

AGGACACCTC AGGACCCATT CTGTGGGTAA ACCTCACAAG TGCAACTACT GTGGACGAAG

CTACAAGCAG CGCAGTTCAC TGGAGGAGCA CAAGGAACGC TGCCACAACT ATCTCCAGAA

TGTCAGCATG GAGGCTGCTG GGCAGGTCAT GAGTCACCAT GTACCTCCTA TGGAAGATTG

TAAGGAACAA GAGCCTATTA TGGACAACAA TATTTCTCTG GTGCCTTTTG AGAGACCTGC

TGTCATAGAG AAGCTCACGG GGAATATGGG AAAACGTAAA AGCTCCACTC CACAAAAGTT

TGTGGGGGAA AAGCTCATGC GATTCAGCTA CCCAGATATT CACTTTGATA TGAACTTAAC

ATATGAGAAG GAGGCTGAGC TGATGCAGTC TCATATGATG GACCAAGCCA TCAACAATGC

AATCACCTAC CTTGGAGCTG AGGCCCTTCA CCCTCTGATG CAGCACCCGC CAAGCACAAT

CGCTGAAGTG GCCCCAGTTA TAAGCTCAGC TTATTCTCAG GTCTATCATC CAAATAGGAT

AGAAAGACCC ATTAGCAGGG AAACTGCTGA TAGTCATGAA AACAACATGG ATGGCCCCAT

CTCTCTCATC AGACCAAAGA GTCGACCCCA GGAAAGAGAG GCCTCTCCCA GCAATAGCTG

CCTGGATTCC ACTGACTCAG AAAGCAGCCA TGATGACCAC CAGTCCTACC AAGGACACCC

TGCCTTAAAT CCCAAGAGGA AACAAAGCCC AGCTTACATG AAGGAGGATG TCAAAGCTTT

GGATACTACC AAGGCTCCTA AGGGCTCTCT GAAGGACATC TACAAGGTCT TCAATGGAGA

AGGAGAACAG ATTAGGGCCT TCAAGTGTGA GCACTGCCGA GTCCTTTTCC TAGACCATGT

CATGTACACC ATTCACATGG GTTGCCATGG CTACCGGGAC CCACTGGAAT GCAACATCTG

TGGCTACAGA AGCCAGGACC GTTATGAGTT TTCATCACAC ATTGTTCGAG GGGAGCACAC

ATTCCACTAG GCCTTTTCAT TCCAAAGGGG ACCCCTATGA AGTAAAGAAC TGCACATGAA

GAAATACCGC ACTTACAATC CCACCTTTCC TCAAATGTTG ACATACCTTT TATTTTTTTT

AATATTATTA CTGTTGATAA TTCTTATTTT GTGGAGGCAG TGTCATTTGC TCTGCCTAAT

TACGATAAGG AAGAAACAGA AGAGAGAAGG GGCGGGAATA TTGTTTCTTT ATCACCTGGC

TTGTTTATTT TGTGGGAATT TAAGAGCAGT CCATTTCTAC CAAGGCATAT CATGCTTTGA

AAAATCACTT GATTCATAAA GATTCACCTA AGAGATTCTG ATTTGCCACT GATATTCAGA

ATTATGATGG AAGACAGGAA AGTTTAGAGT TTTCTGGGCA GGACTTTGGT GGTTTAAAAA

TGGTATAAGT AACTTTATTC TTGAAAGAAG AATGTGTTTC AAACTGTAAA CCAATTTTTT

GTTCTTCAGA GATCATGGAA CACAAACACA TTGTTATTTT CAGTGATAAC TCCTAAGAGG

AGCTGAGTTG TTGTGGGTTC TATGTTTACT TCCCCTATGG AATTTATAAT TCAGTATGTT

TTACACTGTA CCATATAGCA AAACTTTTAA ACTACAGGTA GTTAAGGGCC ACCTACAATA

CATCTGAGGT CCTGTGATCT TATTTTTCTA AACGTAAGCA CTGTTTTTCC ATAGTTTTGA

TGACTGGCAT TTTATAGACA CCCTGGCAGC

Claims

WE CLAIM:

1. A nucleic acid sequence encoding Helios 3 according to SEQ ID NO: 1.

2. An amino acid sequence of Helios 3 according to SEQ ID NO:2.

3. An amino acid sequence of Helios 3 comprising the sequence of SEQ ID NO: 10.

4. An antibody having specific immunoreactivity against the amino acid sequence of SEQ ID NO: 10.

5. Use of an antibody according to claim 4, for the detection or quantification of Helios 3.

6. Use of an antibody according to claim 4, for the diagnosis of lymphohematopoietic disease.

7. A nucleic acid probe that specifically hybridizes to Helios 3 and not Helios 1 or 2.

8. A nucleic acid primer set that specifically amplifies the nucleic acid sequence of claim 1.

9. A method for the diagnosis of lympohematopoietic disease, comprising analyzing a sample for expression of a Helios isoform lacking one or more amino terminal zinc finger; and correlating the expression of said Helios isoform with lymphohematopoietic disease.

10. The method of claim 9, wherein said Helios isoform is Helios 3 having the nucleic acid sequence of SEQ ID NO: 1.