Sox Proteins Modulate Genomic Specificity of B-catenin Regulated Transcription in the Developing Gut

项目总结/摘要 该提案将测试SOX转录因子（TF）调节基因组的假设 Wnt/β-catenin（BCAT）介导转录在早期肠道发育中的特异性和确定 潜在的分子机制。Wnt信号对消化系统基因表达的调控 发育、稳态和疾病，其中它是重要的治疗靶点。而核心WNT 尽管转录机制已经得到很好的研究，但如何选择细胞特异性靶基因仍然是最重要的问题之一。 外地尚未解决的重要问题。目前的教条是，典型的Wnt稳定细胞质BCAT， 易位到细胞核并与四种TCF/LEF HMG盒TF之一相互作用以刺激转录。 然而，所有的TCF都与几乎相同的共有位点结合，这表明它们本身不能解释TCF的多样性。 转录反应。利用非洲爪蟾胚胎的互补优势， 人类多能干细胞（hPSC），我们已经积累了令人信服的证据，SOX HMG盒TF 在肠道发育早期调节Wnt/BCAT介导的转录的基因组特异性。我们 初步的ChIP-seq数据和功能分析表明，不同的SOX TF可以招募BCAT， 以组织特异性方式增强。在一些增强子SOX和BCAT协同激活转录 独立于TCF。其他增强子似乎被SOX、BCAT和TCF共同占据，这表明三级增强子可能是由BCAT和TCF共同占据的。 SOX和TCF可能合作或竞争结合DNA和BCAT以激活或抑制 转录。这些数据提示了新的调节机制，并表明SOX可能广泛分布于 调节Wnt反应的未被重视的因素。我们建议检验这一假设，目的如下： 目的1：检验SOX调节BCAT向谱系特异性增强子的基因组募集的假设。 目的2：确定Sox 17和Bcat如何共同调节Wnt应答增强子以控制空间限制性 胚胎中的转录。 目的3：确定SOX-BCAT-TCF复合物与DNA相互作用的生化机制。 这些研究将揭示SOX-BCAT调控GRN的肠道发育机制，为研究GRN的功能提供新的思路 细胞特异性Wnt介导的转录如何在发育和疾病中调节。

PROJECT SUMMARY/ABSTRACT This proposal will test the hypothesis that SOX transcription factors (TFs) modulate the genomic specificity of Wnt/Beta-catenin (BCAT) mediated transcription in early gut development and determine the underlying molecular mechanisms. Wnt signaling regulates gene expression in digestive system development, homeostasis and disease, where it is an important therapeutic target. While the core Wnt transcriptional machinery is well studied, how cell-specific target genes are selected remains one of the most important unresolved issues in the field. Current dogma is that canonical Wnt stabilizes cytoplasmic BCAT, which translocates to the nucleus and interacts with one of four TCF/LEF HMG-box TFs to stimulate transcription. However, all TCFs bind to nearly identical consensus sites indicating they alone cannot account for the diversity of transcriptional responses. Using the complementary advantages of Xenopus embryos and differentiating human pluripotent stem cells (hPSC), we have accumulated compelling evidence that SOX HMG-box TFs modulate the genomic specificity of Wnt/BCAT-mediated transcription during early gut development. Our preliminary ChIP-seq data and functional analyses suggests that different SOX TFs can recruit BCAT to distinct enhancers in a tissue specific manner. On some enhancers SOX and BCAT synergistically activate transcription independent of TCFs. Other enhancers appear to be co-occupied by SOX, BCAT and TCFs, suggesting tertiary complexes where SOX and TCF might cooperate or compete to bind DNA and BCAT to activate or represses transcription. These data suggest novel regulatory mechanisms and indicate that SOXs may be wide-spread unappreciated factors regulating Wnt responses. We propose to test this hypothesis with the following aims: Aim 1: Test the hypothesis that SOXs regulate the genomic recruitment of BCAT to lineage specific enhancers. Aim 2: Determine how Sox17 and Bcat coregulate Wnt-responsive enhancers to control spatially restricted transcription in the embryo. Aim 3: Determine the biochemical mechanisms by which SOX-BCAT-TCF complexes interact on DNA. These studies will reveal the SOX-BCAT regulated GRN of gut development and provide a new paradigm for how cell-specific Wnt-mediated transcription is regulated in development and disease.