Transcriptional Activation by Wnt Signaling

Wnt 信号转导的转录激活

• 批准号: 7895917
• 负责人: KENNETH M CADIGAN
• 金额: $ 28.95万
• 依托单位: UNIVERSITY OF MICHIGAN AT ANN ARBOR
• 依托单位国家: 美国
• 财政年份: 2008
• 资助国家: 美国
• 起止时间: 2008-08-01 至 2012-07-31
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7895917
• 关键词: Acetylation; Address; Adult; Animals; Attention; Binding; Binding Proteins; Binding Sites; Bioinformatics; Biological; Cell Communication; Cell Culture Techniques; Cell Maintenance; Cell Nucleus; Cells; Chimeric Proteins; Chromatin; Chromatin Remodeling Factor; Chromatin Structure; Computer Simulation; Consensus Sequence; DNA; DNA-Binding Proteins; Data; Development; Drosophila genus; Epigenetic Process; Family; Family Dasypodidae; Felis catus; Gene Activation; Gene Expression Regulation; Genetic Transcription; Genome; Glycoproteins; Goals; Histone Acetylation; Histones; Human; In Vitro; Indium; Lead; Link; Location; Maintenance; Malignant Neoplasms; Mediating; Methods; Modeling; Modification; Molecular; Mutagenesis; N-terminal; Names; Nuclear; Pathway interactions; Pattern; Play; Process; Reporter; Response Elements; Role; Sequence-Specific DNA Binding Protein; Signal Pathway; Signal Transduction; Site; Site-Directed Mutagenesis; Specificity; Stem cells; System; Tail; Testing; Tissues; Trans-Activators; Transcription Repressor/Corepressor; Transcriptional Activation; Transgenic Organisms; Work; arm; beta catenin; cell type; chromatin modification; fly; genome-wide; histone acetyltransferase; member; promoter; stem cell population; tissue regeneration

DESCRIPTION (provided by applicant): Secreted glycoproteins of the Wnt family act through an evolutionarily conserved signaling cascade which promotes the nuclear accumulation of beta-catenin, which interacts with members of the TCF family of DNA-binding proteins to activate target gene transcription. TCFs binds to specific sequences, but the consensus is so loose that potential TCF binding sites can be found throughout the genome. Despite this, we find that TCF is bound to specific locations in Wnt targets, corresponding to Wnt response elements (WREs). Systematic mutagenesis of a WRE revealed the presence of additional motifs that act with TCF binding sites to mediate activation by Wnt signaling. These motifs (called Helper sites) are found in several other WREs, and genome-wide searches for conserved TCF/Helper site clusters have identified other putative WREs. The functional significance of the Helper sites in these elements will be tested. The molecular mechanism of how Helper sites interact with TCF binding sites will be explored, and the trans-acting factor(s) that bind to it will be characterized. Binding of beta-catenin to TCF converts it from a transcriptional repressor to an activator. We have found that Wnt signaling promotes histone acetylation throughout target loci, which is correlated with activation of transcription. This widespread modification appears to be required to antagonize the action of factors that silence Wnt targets. The mechanisms and relationship between these processes will be explored in detail. Our data indicates that the transcriptional switch at Wnt targets involves changes in chromatin structure far beyond what was previously recognized. PROJECT NARRATIVE: The Wnt signaling pathway plays important roles in cell fate decisions during development, and is required for the maintenance of stem cell populations in adult tissues. Misregulation of the pathway plays a causal role in many human cancers. Our studies to understand the role of motifs besides TCF sites that contribute to WRE function will lead to better bioinformatic methods to identify Wnt targets in many important biological contexts. Our work on the role of chromatin modifications in regulating the TCF transcriptional switch will serve as a paradigm to study these processes in mammalian systems.

描述（由申请人提供）： Wnt家族的分泌糖蛋白通过进化保守的信号级联反应促进β-catenin的核积累，该蛋白与DNA结合蛋白的TCF家族相互作用以激活靶基因转录。 TCF与特定序列结合，但共识是如此松散，以至于在整个基因组中都可以找到潜在的TCF结合位点。尽管如此，我们发现TCF与Wnt目标中的特定位置绑定，对应于Wnt响应元素（WRES）。 WRE的系统诱变揭示了存在与TCF结合位点起作用的其他基序，以通过Wnt信号传导介导激活。这些图案（称为辅助站点）在其他几个WRE中都发现，并且全基因组对保守的TCF/Helper Site群集搜索已经确定了其他推定的WRES。这些元素中帮助手位点的功能意义将进行测试。将探索助手位点如何与TCF结合位点相互作用的分子机制，并将表征与其结合的跨作用因子。 β-catenin与TCF的结合将其从转录阻遏物转换为激活剂。我们发现WNT信号传导促进整个靶基因座的组蛋白乙酰化，这与转录的激活相关。这种广泛的修改似乎是必需的，以拮抗沉默Wnt目标的因素的作用。这些过程之间的机制和关系将进行详细探讨。我们的数据表明，Wnt目标的转录开关涉及染色质结构的变化，远远超出了先前认识的范围。项目叙述：WNT信号通路在发育过程中在细胞命运决策中起着重要作用，并且是维持成人组织中干细胞种群所必需的。途径的不正体在许多人类癌症中起因果作用。我们的研究以了解有助于WRE功能的TCF站点以外的基序的作用将导致更好的生物信息学方法在许多重要的生物学环境中识别Wnt靶标。我们在调节TCF转录开关中的作用方面的作用将是研究哺乳动物系统中这些过程的范例。