JP4509656B2 - Method for screening compound that inhibits formation of STAT3, NF-κBp65, and p300 complex - Google Patents

Description

  The present invention relates to a method for screening a compound that inhibits the formation of STAT3, NF-κB p65, and p300 complex, particularly a compound that has an anti-inflammatory effect by inhibiting the formation of STAT3, NF-κB p65, and p300 complex. It is about.

  IL-6 is called an inflammatory cytokine, and is known to exhibit various physiologically active actions in the inflammatory reaction along with IL-1 and TNFα. Akira outlined the functions and structures of NF-IL6 and STAT3, transcription factors that activate IL-6, and the promoters of genes involved in inflammation (IL-6, IL-8, ICAM-1, etc.) Above, it is described that the arrangement of the NF-IL6 (now called C / EBPβ) binding region and the NF-κB binding region is universally seen (see Non-Patent Document 1).

  Serum amyloid A protein (SAA) is one of the acute inflammatory proteins and is known as a marker of inflammatory reaction, and is useful for quantifying the inflammatory state and determining the therapeutic effect of antibiotics against pneumonia. An arrangement of C / EBPβ binding region and NF-κB binding region is also found on the promoter of human SAA1 gene. Betts and colleagues report that the synergistic expression of SAA by IL-6 and IL-1 is due to the activation of C / EBPβ by IL-6 and the activation of NF-κB by IL-1. (See Non-Patent Document 2).

  The promoter and exon DNA sequences of the human SAA1 gene are already known, and the promoter region is located at positions −796 to +24 of the SAA1 gene sequence (FIG. 1, SEQ ID NO: 1) (for example, non-patent literature) (See 2) (Here, position +1 represents the starting point of the structural gene sequence of the SAA1 gene, and the first of SEQ ID NO: 1 corresponds to position -796 of the SAA1 gene sequence).

  Recently, anti-cytokine therapy has been clinically applied to patients with rheumatoid arthritis. IL-6 inhibition treatment normalizes CRP, an acute inflammatory protein. Zhang et al. Examined the binding of STAT3 to a GAS-like sequence (TTCCCGAA) reported as a known binding region of STAT3 found in the promoter of human CRP. In gel shift assay experiments, anti-STAT3 (C-20 ) The shift band was confirmed by the antibody, and it was confirmed that STAT3 was directly bound (see Non-Patent Document 3).

  However, normalization of SAA in blood is also observed by IL-6 inhibition treatment. Unlike the case of CRP, SAA does not have a known binding region of STAT3, so this phenomenon was insufficient with conventional explanations.

  Sakakibara et al. Examined the mechanism of SAA normalization using three types of hepatoma cells derived from human liver cancer, confirmed that IL-6 is essential for the expression of SAA synergistic effects by combining cytokines, It has been shown that STAT3, which has not been said to be involved in the past, is involved in SAA expression (see Non-Patent Document 4). However, as described above, the conventionally reported binding region of STAT3 is not found on the promoter of the human SAA1 gene.

  When STAT3 regulates transcriptional activity, there are two important phosphorylation sites, one is the 705th tyrosine and the other is the 727th serine (see, for example, Non-Patent Document 1). STAT3 is known to dimerize and translocate to the nucleus by tyrosine phosphorylation. Wen et al. Showed that transcriptional activation by STAT3 does not maximize transcriptional activation without phosphorylation of the 727th serine, but does not affect the binding of transcription factors to DNA (Non-patent Document 5). reference). However, the role of serine is still not fully understood, and the role of serine phosphorylation of STAT3 is completely unknown even if it is placed in the transcriptional regulatory mechanism of SAA.

  Recently, attention has been paid to the function and importance of p300 / CBP, which is a transcription coupling factor (see, for example, Non-Patent Document 6). It is known that a transcription coupling factor binds to various transcription factors to form a complex, and promotes transcription by histone acetylation. Although STAT3 has been reported to bind to p300 (see, for example, Non-Patent Document 7), the relationship between STAT3 and p300 / CBP in SAA expression is also unclear.

  In other words, analyzing the transcriptional regulatory mechanism of STAT3 in SAA expression that is currently unknown leads to analysis of the mechanism of inflammation in vivo, and if it can inhibit its function, it can be widely applied to inflammatory reactions in general. It is expected to be possible.

  NF-κB decoy is a therapeutic agent that inhibits the mechanism of inflammation (see, for example, Patent Document 8). This aims to suppress inflammation by directly inhibiting the binding of NF-κB, which is the origin of the mechanism of inflammation, to the promoter region of the SAA1 gene.

  The transcriptional regulation mechanism of the protein said so far refers to the experimental results using the yeast model organism. In other words, it is a model in which one transcription factor activated by a certain stimulus directly binds to DNA, which is a specific sequence, enhances transcription, and causes protein expression. The drug developed with reference to this model is the NF-κB decoy described above. However, a drug developed based on this model completely suppresses a necessary level of defense reaction in vivo, and various strong side effects are expected. In fact, NF-κB decoy has a drawback in that it is highly toxic such as liver damage when administered systemically, and its use is limited only to intraarticular injection.

  On the other hand, in mammalian cells, a more complicated transcriptional regulatory mechanism is expected, but it has not been fully searched.

Shizuo Akira, transcription factor NF-IL6 and STAT3 protein involved in cytokine signal transduction Nucleic acid Enzyme 41 (8) 1237-1248 (1996) Betts, JC, Edbrooke, MR, Thakker, RV and Woo, P. The human acute-phase serum amyloid A gene family: structure, evolution and expression in hepatoma cells.Scand. J. Immunol. 34 (4), 471-482 (1991) D. Zhang, M. Sun, D. Samols, I. Kushner, STAT3 participates in transcriptional activation of the C-reactive protein gene by Interleukin-6. J Biol Chem 271,9503-9509 (1996) Hagihara K, Nishikawa T, Isobe T, Song J, Sugamata Y, Yoshizaki K IL-6 plays a critical role in the synergistic induction of human serum amyloid A (SAA) gene when stimulated with proinflammatory cytokines as analyzed with an SAA isoform real- time quantitative RT-PCR assay system. Biochem. Biophys. Res. Commun. 314, 363-369 (2004) Wen, Z. and Darnell, J. E. Jr. Mapping of STAT3 serine phosphorylation to a single residue (727) and evidence that serine phosphorylation has no influence on DNA binding of STAT1 and STAT3.Nucleic Acids Res. 25, 2062-2067 (1997) Hiroaki Kawasaki and Kazutaka Yokoyama, Coactivator function of the transcriptional control tower p300 / CBP, experimental medicine 17 (3) 219-228 (1999) Nakashima, K. et al. Synergistic signaling in fetal brain by STAT3-Smad1 complex bridged by p300. Science 284, 479-482 (1999) Tomita T et al. (1999) Suppressed severity of collagen-induced arthritis by in vivo transfection of nuclear factor kappaB decoy oligodeoxynucleotides as a gene therapy.Arthritis Rheum 42, 2532-2542

  Here, we have found that the formation of a complex of transcription factors STAT3, NF-κB p65, and transcription coupling factor p300 is important in the mechanism of inflammation. Furthermore, it has also been found that if this complex formation is inhibited, inflammation can be suppressed. The advantage of this approach of inhibiting complex formation is that it is possible to regulate the inflammatory response while leaving the defense response necessary for the body.

  The object of the present invention is to provide a screening method for compounds that inhibit the formation of STAT3, NF-κB p65, and p300 complexes based on the above findings.

More particularly, the present invention is a method of screening for compounds that inhibit the formation of STAT3, NF-κB p65, and p300 complexes comprising:
(A) contacting a STAT3, NF-κB p65, and p300 complex dissociation preparation in solution with a test compound;
(B) reducing the salt concentration of the solution to a salt concentration at which STAT3, NF-κB p65, and p300 complexes are formed,
(C) The present invention relates to a screening method comprising a step of detecting the presence or absence of formation of the complex using an oligonucleotide probe for detecting STAT3, NF-κB p65, and p300 complex.

  Furthermore, the present invention relates to the above screening method wherein the compound has an anti-inflammatory action.

  As used herein, “STAT3, NF-κB p65, and p300 complex” is obtained from a mammalian cell after stimulation with IL-6 and IL-1β, preferably a human liver cancer-derived cell line, most preferably a HepG2 cell. Refers to the complex of STAT3, NF-κB p65, and p300 contained in the nuclear extract. This complex can be purified and isolated by conventional methods known to those skilled in the art.

  As used herein, “STAT3, NF-κB p65, and p300 complex dissociation preparation” refers to an increase in the salt concentration of an appropriate salt concentration solution containing the STAT3, NF-κB p65, and p300 complex. It refers to the resulting preparation that exists in a dissociated state of the complex. It is possible to test whether the test compound inhibits the formation of the complex by mixing the test compound with this preparation and then reducing the salt concentration. A suitable salt concentration at which the STAT3, NF-κB p65, and p300 complex forms a complex is 40-150 mM, preferably 50-100 mM, most preferably 60 mM. A suitable salt concentration for dissociating the complex is 300-1000 mM, preferably 300-500 mM, most preferably 400 mM. Any conventional salt can be used to obtain an appropriate salt concentration, with KCl being preferred. In order to change the salt concentration, a conventional method such as dialysis can be used.

  These STAT3, NF-κB p65, and p300 complexes, and STAT3, NF-κB p65, and p300 complex dissociation preparations can be stored by conventional methods, such as -80 ° C. freezing storage. It can also be stored refrigerated by adding ingredients, and can be made part of a screening kit by subdividing the preparation into vials or the like.

  In the present specification, “an oligonucleotide probe for detecting STAT3, NF-κB p65, and p300 complex” means SAA1 containing an NF-κB binding region capable of binding to STAT3, NF-κB p65, and p300 complex. An oligonucleotide fragment of a promoter. This oligonucleotide fragment preferably contains the oligonucleotide fragment SAA1 (-196 to -73), and most preferably the oligonucleotide fragment SAA1 (-196 to -73). In addition, the probe may be subjected to treatment by a conventional method for facilitating detection, such as biotinylation, as necessary.

As used herein, “IL-6 and IL-1β stimulation” refers to incubation of cells in a culture medium containing appropriate concentrations of IL-6 and IL-1β. The concentration of IL-6 is 1 to 100 ng / ml, preferably 10 ng / ml, and the concentration of IL-1β is 0.05 to 10 ng / ml, preferably 0.1 ng / ml.
(The invention's effect)

  According to the screening method of the present invention, a compound having low toxicity and effective in treating various inflammatory diseases can be obtained by inhibiting the formation of a complex of STAT3, NF-κB p65, and p300.

  The present invention will be described in more detail with reference to the following examples, but these show preferred embodiments of the present invention and do not limit the scope of the present invention.

(Example 1)
1) Importance of the formation of STAT3, NF-κB p65, and p300 complex in the mechanism of inflammatory response induced by IL-6 + IL-1: Experiment using SAA1 promoter region, which is one of acute inflammatory proteins.

SAA1 promoter region -796 to +24 (FIG. 1, SEQ ID NO: 1) was incorporated into pGL3 basic vector at Mlul and Xhol sites to prepare SAA1 promoter luciferase vector. The cells were transferred to HepG2 cells (2 × 10 ⁵ cells) cultured for 24 hours, and after 72 hours culture, IL-6 and IL-1β stimulation (IL-6 10 ng / ml, IL-1β 0.1 ng / ml was cultured in cells. Injection). Since the synergistic enhancement effect of SAA1 transcriptional activity by IL-6 + IL-1β stimulation was observed to increase after 3 hours, it was decided to measure 3 hours after cytokine stimulation in the subsequent experiments.

  As shown in FIG. 2, the luciferase activity representing the transcriptional activity of SAA1 was slight with each cytokine alone, but IL-6 + IL-1β stimulation showed a synergistic increase in activity of about 10 to 12 times. It is known that tyrosine phosphorylation at position 705 plays an important role in the activation of STAT3. By phosphorylating the 705th tyrosine of the STAT3 protein, STAT3 forms a dimer, moves into the nucleus, and activates transcription of the target gene. In other words, substitution of 705th tyrosine with phenylalanine suppresses activation of STAT3 by phosphorylation. Therefore, pEF-BOS dominant negative STAT3 in which the 705th tyrosine encoded by the wild-type STAT3 gene was changed to phenylalanine or pEF-BOS wild-type STAT3 was simultaneously introduced into HepG2 cells. When wild-type STAT3 was overexpressed, luciferase activity was enhanced by 30-40 times or more, but when dominant-negative STAT3 was overexpressed, luciferase activity was completely lost.

  Based on the above, it was considered that STAT3 is essential for transcriptional activation in the SAA promoter region.

  Next, the luciferase activity of pGL3-SAA1 (-796 to +24) with the NF-κB binding region (-95 to -85) deleted using the Quick Change Site-Directed Mutagenesis Kit (STRATAGENE) When measured, the activity completely disappeared. At the same time, when wild-type STAT3 was overexpressed and examined, no potentiating effect by STAT3 was observed, and the activity remained lost (FIG. 3).

  Studies with a rat γ-fibrinogen promoter indicate that a sequence called TCC is required for NF-κB p65 binding in the NF-κB binding region (see Non-Patent Document 2). Based on the results, a variant called (GGGACTTGTAC) (SEQ ID NO: 2) was created for the NF-κB binding region (GGGACTTTCCC) of SAA1. The activity disappeared in the mutant, and no potentiation by STAT3 was observed (FIG. 3).

  This indicates that STAT3 enhances the transcriptional activity of SAA1 via the NF-κB binding region, but that requires the binding of NF-κB p65 to the NF-κB binding region.

  Recently, it has been reported that a transcription coupling factor associates with a transcription factor bound to a target gene, changes the chromatin structure of the oligonucleotide by histone acetyltransferase activity, and regulates transcription. The importance of p300, one of its transcriptional coupling factors, has been reported (see Non-Patent Document 3, for example). However, in the experimental results using the expression of luciferase activity as an index, only overexpression of wild-type p300 has been reported. The transcriptional activity of SAA1 was not enhanced. However, overexpression of wild-type STAT3 in addition to wild-type p300 further enhanced the activity of STAT3 to enhance transcriptional activity. Interestingly, p300 further enhanced the transcriptional activity of SAA1 depending on the expression level of STAT3 (FIG. 4). There are three important regions of p300, of which C / H1 and C / H3 regions bind to various transcription factors. The p300 (ΔC / H3) mutant lacking the C / H3 region was unable to induce further enhancement of STAT3 (Fig. 4), indicating that STAT3 and p300 are mediated through the C / H3 region of p300. It was shown that they are combined.

  These results indicate that the formation of a complex of STAT3, NF-κB p65, and p300 by IL-6 + IL-1 stimulation is important in enhancing the expression of SAA1, an acute inflammatory protein by cytokines. It was.

  2) Formation of STAT3, NF-κB p65, and p300 complex is a common process in the mechanism of inflammation induced by IL-6 + IL-1 stimulation.

  From the result of the above 1), it is possible that the formation of STAT3, NF-κB p65, and p300 complex occurs specifically in the SAA1 gene. Therefore, it was confirmed that the complex was formed in the nucleus by using an immunoprecipitation method that is generally used as a method for showing protein binding.

  Anti-STAT3 (C-20) antibody was added to 200-300 μg of HepG2 cell nuclear extract 30 minutes after cytokine stimulation, and mixed overnight at 4 ° C. Next, the complex of the antibody and the nuclear extract was adsorbed by adding Protein-A Sepharose beads (Amersham) and precipitated by light centrifugation. The operation of discarding the supernatant, adding the reaction solution to the precipitate, and precipitating by centrifugation was repeated 4 times. Finally, a reaction solution for separation was added to the precipitate, the antibody and the nuclear extract were separated from Protein-A Sepharose bead, and the protein was subjected to electrophoresis. Electrophoresis was performed by SDS-PAGE (SDS-polyacrylamide electrophoresis) using 6-7.5% polyacrylamide gel. This was treated with each antibody and analyzed by Western blot. Anti-NF-κB p65 antibody (Upstate biothechnology), anti-NF-κB p50 antibody (Santa Cruz), or anti-STAT3 (C-20) antibody (Santa Cruz), anti-phospho-STAT3 Y705 antibody (Cell Signaling Technology ), Anti-p300 antibody (Upstate biothechnology) was used.

  With IL-6 or IL-1 stimulation alone, no NF-κB p65 band was detected in the protein co-precipitated with anti-STAT3 (C-20) antibody. Only when IL-6 + IL-1β stimulation was performed, a band of NF-κB p65 was clearly detected (FIG. 5). On the other hand, the band of NF-κB p50 could not be detected (data not shown).

  In the case of p300, the band of p300 in the protein precipitated with the anti-STAT3 (C-20) antibody was clearly enhanced in IL-6 + IL-1β stimulation as compared with no stimulation (FIG. 6). Since the binding of STAT3 and p300 was shown from the same nuclear extract as in FIG. 5, it was shown that a complex of STAT3, NF-κB p65, and p300 was formed.

  From the above results, IL-6 + IL-1β stimulation stimulates STAT3 and NF-κB p65 and p300 to form a complex, and further, the complex binds to the target gene SAA1 promoter. It was found that a synergistic expression effect was produced.

(Example 2)
A screening method for compounds that inhibit STAT3, NF-κB p65, and p300 complex formation.
1) Preparation of STAT3, NF-κB p65, and p300 complex dissociation preparations

According to the method described in Example 1, nuclear extracts containing STAT3, NF-κB p65, and p300 complex were removed from HepG2 cells after IL-6 and IL-1β stimulation. Next, the obtained nuclear extract was injected into Slide-A-Lyzer 3.5kMW (Pierce) and dialysate (20 mM Hepes (pH7.8), 50 mM KCl, 12.5 mM MgCl ₂ , 1 mM EDTA, 1 mM dithiothreitol). , 0.1% NP-40, 20% glycerol) and dialyzed at 4 ° C. for 1 hour. Since the nuclear extract uses a reaction solution containing 400 mM KCl for purification, the STAT3, NF-κB p65, and p300 complexes contained in the nuclear extract are once dissociated, and the STAT3, NF-κB p65, and p300 are dissociated. A complex dissociation preparation will be obtained (hereinafter simply referred to as “complex dissociation preparation” herein).

  The resulting complex dissociation preparation will again form a complex with STAT3, NF-κB p65, and p300 by reducing the salt concentration to 50 mM KCl.

When a dialysis membrane of 10 kDa or more was used during dialysis, a complex was not formed even when the salt concentration was lowered. Therefore, it was found that the dialysis membrane had to have a cutoff value of 3.5 kDa or less.
2) Preparation of oligonucleotide probes for detecting STAT3, NF-κB p65, and p300 complexes 2-1) Examination of oligonucleotides that bind to STAT3, NF-κB p65, and p300 complexes

To determine the oligonucleotides that can be used to detect STAT3, NF-κB p65, and p300 complexes, DNA affinity chromatography studies were performed.
Briefly, the reaction mixture (10 mM Tris-Cl (pH 7.5), 1 mM EDTA, 4% glycerol, 5 mM dithiothreitol, 60 mM) was added to 200 μg of the nuclear extract from HepG2 cells obtained in Example 2, 1). NaCl, 100 ng / μl bovine serum albumin, 600 ng / μl poly (dI-dC)), and 1 μg of 5′-end oligonucleotide labeled with biotin, finally adjusted to a volume of 500 μl, 25 ° C., 30 minutes Reacted. 50 μl of streptavidin-Dynabeads (Dynal) was added to the reacted sample and reacted at 4 ° C. for 30 minutes. Next, Dynabeads reacted with oligonucleotides were collected with a magnet, washed with a reaction solution, proteins were extracted, and analyzed by Western blotting using each specific antibody.

First, as a positive control for an oligonucleotide capable of detecting STAT3, a 15-base GAS sequence (CATTTCCCGTAAATC), which was confirmed to bind directly to STAT3, was used, and a STAT3 band was clearly detected. Therefore, when SAA1 (-105 to -75) containing a 30-base NF-κB binding region was first examined, the NF-κB p65 band was clearly detected, but the STAT3 band was not clear. There wasn't.
Since the protein forming the complex was expected to be enormous, further investigation was performed considering that a sufficiently long oligonucleotide was required for binding to DNA. When the nucleotide fragment SAA1 (-196 to -73) was used, bands of STAT3 and NF-κB p65 were clearly detected (FIG. 7). In other words, it was shown that STAT3 binds to DNA by forming a complex with other transcription factors, unlike when STAT3 binds directly to DNA alone.

  From the above results, it was considered important to include oligonucleotide 124 base SAA1 (-196 to -73) as an oligonucleotide probe for detecting STAT3, NF-κB p65, and p300 complex. Therefore, in the following experiment, oligonucleotide 124 base SAA1 (-196 to -73) was used.

  2-2) Using the oligonucleotide 124 base SAA1 (-196 / -73) determined in the above 2-1), it was reacted with the nuclear extract as follows.

  Next, 10 μg of the nuclear extract obtained according to the method described in Example 1 was added to the reaction solution (10 mM Tris-Cl (pH 7.5), 1 mM EDTA, 4% glycerol, 5 mM dithiothreitol, 60 mM NaCl 100 ng / μl). Bovine serum albumin, 600 ng / μl poly (dI-dC)) and the synthesized 5 fmol biotinylated oligonucleotide SAA1 (−196 to −73) were mixed, adjusted to a final volume of 20 μl in the reaction, then 25 The reaction was performed at ° C for 30 minutes. Subsequently, the reaction product was subjected to polyacrylamide electrophoresis, and color was developed using a biotin avidin system (LightShift (registered trademark) Chemiluminescent EMSA kit (Pierce)) according to the instruction manual.

As a result, it was confirmed that the biotinylated oligonucleotide can detect STAT3, NF-κB p65, and p300 complex (FIG. 8). This biotinylated oligonucleotide SAA1 (-196 to -73) was used as an oligonucleotide probe for detection of STAT3, NF-κB p65, and p300 complex.
3) Screening of STAT3, NF-κB p65, and p300 complex inhibitors with biotinylated oligonucleotide SAA1 (-196 to -73) 3-1) Screening procedure

STAT3, NF-κB p65, and p300 complex dissociation preparation obtained in Example 2, 1) (20 mM Hepes (pH 7.8), 50 mM KCl, 12.5 mM MgCl ₂ , 1 mM EDTA, 1 mM dithiothreitol, 0.1 3 μl of (% NP-40, 20% glycerol) is mixed with 1-10 μl of the test compound. The salt concentration of the mixture is dialyzed to 50 mM KCl and reacted at 37 ° C. for 60 minutes. Next, 4-13 μl of the reaction product was added to the reaction solution of Example 1 (10 mM Tris-HCl (pH 7.5), 1 mM EDTA, 4% glycerol, 5 mM dithiothreitol, 60 mM NaCl 100 ng / μl bovine serum albumin, 600 ng / μl poly (dI-dC)) and 5 fmol biotinylated oligonucleotide SAA1 (−196 to −73), adjust the final volume to 20 μl with the reaction, and then react at 25 ° C. for 30 minutes. The reaction is subjected to polyacrylamide electrophoresis and tested for color development using a biotin avidin system (LightShift® Chemiluminescent EMSA kit (Pierce)). When no color development is observed, it indicates that the test compound inhibited the formation of STAT3, NF-κB p65, and p300 complex.
3-2) Compounds subject to the screening method of the present invention

  Using the specific antibody against NF-κB p65 as a test compound (reaction conditions: 1 hour at 37 ° C.), the screening method of 3-1) above was performed, and the complex was detected in the same manner. As a result, STAT3, NF A shift band indicating that a specific antibody against NF-κB p65 was bound to -κB p65 and p300 complex was confirmed. The shift band indicates that the electrophoretic mobility of the complex was slowed by binding of the specific antibody to NF-κB p65 that directly binds to DNA. This suggests that NF-κB p65 binds directly to DNA on the SAA1 promoter, but specific antibodies to NF-κB p65 do not inhibit the formation of STAT3, NF-κB p65, and p300 complexes. Show. A shift band of the complex was also confirmed in the specific antibodies against NF-κB p50 and C / EBPβ having a binding region on biotinylated oligonucleotide SAA1 (-196 to -73).

  On the other hand, when STAT3 Ser727 phosphorylated antibody was used as a test compound and screening was carried out in the same manner, it was confirmed that formation of STAT3, NF-κB p65, and p300 complex was inhibited (FIG. 9). It has been reported that the 727th serine of STAT3 is conventionally necessary for maximizing transcriptional regulation, but is not necessary for binding of STAT3 to DNA (see, for example, Non-Patent Document 4). Since the STAT3 Ser727 phosphorylated antibody is directed against the phosphorylated 727th serine, this indicates that the STAT3 727th serine is important for STAT3, NF-κB p65, and p300 complex formation. Suggests.

  The above indicates that the screening method of the present invention inhibits STAT3, NF-κB p65, and p300 complex formation by inhibiting STAT3 function, which is the key to STAT3, NF-κB p65, and p300 complex formation. It is shown that it is particularly suitable for screening of the compound.

  Conventionally, in the known direct binding region GAS-like sequence of STAT3 (TTCC (C / G) GGAA), the STAT3 (C20) antibody, which is an antibody against the C-terminus of STAT3, causes a shift band of the STAT3 / DNA complex. It is reported that it is recognized (for example, refer nonpatent literature 5). The shift band indicates that the electrophoretic mobility of STAT3 and the DNA complex is slowed by binding of the specific antibody to STAT3 that directly binds to DNA. However, in this screening method, STAT3 (C20) antibody does not inhibit the formation of this STAT3, NF-κB p65, and p300 complex (FIG. 10). This suggests that in this phenomenon, the target site of the STAT3 (C20) antibody may be covered with another protein due to complex formation. Furthermore, we show that STAT3 does not directly bind to DNA on the SAA1 promoter as is known in the art. From this, it is clear that the screening method of the present invention is suitable for examination when STAT3, NF-κB p65, and p300 bind to DNA in the vicinity of the NF-κB binding region by complex formation.

  In order to confirm that this result was not caused by a nonspecific reaction, the function of serine phosphorylation of STAT3 was confirmed. pGL3-SAA1 (-796 to +24) was forced to express an expression vector of pEF-BOS STAT3 S727A in which serine 727 of STAT3 was replaced with alanine. The method is the same as in FIG. As a positive control, wild type STAT3 was forcibly expressed.

As shown in FIG. 11, when wild-type STAT3 was overexpressed, a synergistic expression effect of luciferase activity by IL-6 + IL-1β stimulation was observed, but when STAT3 in which serine was replaced with alanine was overexpressed The enhancement effect observed with wild-type STAT3 disappeared, and the activity was further suppressed by about 25%. That is, it was confirmed that phosphorylation of serine is important in terms of function.
In other words, this screening method not only showed that one of the functions of serine phosphorylation of STAT3, which was not involved in DNA binding and whose role was unknown, is necessary for complex formation. It has been shown to be a target in inhibiting the formation of complexes.
From the above, it seems that this screening method can easily search for compounds that inhibit the formation of the complex.

  In the inflammatory response, various inflammation-inducing substances are produced and transcription factors such as NF-κB and C / EBPβ are activated. However, even when multiple stimuli are added, the promoter of DNA that ultimately encodes SAA1 SAA expression does not occur unless a complex of STAT3, NF-κB p65, and p300 is formed. The sequence of NF-κB binding region (-95 to -85) downstream of the C / EBPβ binding region (-188 to -175) found in oligonucleotide SAA1 (-196 to -73) is a protein ( IL-6, IL-8, ICAM-1, etc.) (see non-patent document 6, for example). That is, the inhibitory substance obtained by the screening method using this oligonucleotide can be widely applied not only to suppress the expression of SAA but also to the screening of various compounds having a broad anti-inflammatory action.

It is a figure which shows the nucleotide sequence of the promoter region of SAA1. It is a figure which shows that STAT3 is required for the transcriptional activity of SAA1 and SAA2. It is a figure which shows that NF-κB binding region is required for transcriptional activity of SAA1. FIG. 3 shows that p300 enhances the transcriptional activity of SAA1 depending on the expression level of STAT3. It is a figure which shows that STAT3 and NF-κB p65 form a complex. It is a figure which shows that STAT3 and p300 form a complex. It is a figure which shows that STAT3 and NF-κB p65 are detected by oligonucleotide fragment SAA1 (−196 / −73). It is a figure which shows that the band of a complex is detected by oligonucleotide 124 base SAA1 (-196 / -73). It is a figure which shows that the phosphorylated antibody of the 727th serine of STAT3 inhibits complex formation. It is a figure which shows that complex formation is not inhibited in STAT3 (C20) antibody. It is a figure which shows that phosphorylation of the 727th serine of STAT3 is required for transcriptional activity.

Claims (2)

A method of screening for compounds that inhibit the formation of STAT3, NF-κB p65, and p300 complexes, comprising:
(A) contacting a STAT3, NF-κB p65, and p300 complex dissociation preparation in solution with a test compound;
(B) reducing the salt concentration of the solution to a salt concentration at which STAT3, NF-κB p65, and p300 complexes are formed,
(C) A screening method comprising a step of detecting the presence or absence of formation of the complex using an oligonucleotide probe for detecting STAT3, NF-κB p65, and p300 complex.   The screening method according to claim 1, wherein the compound has an anti-inflammatory action.

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