'Thyroid Hormone and the Gut'

超出提供的空间。甲状腺激素(T3)是肠上皮结构和功能最有效的调节剂之一。T3似乎在肠道上皮生物学的几乎所有方面都起着至关重要的作用，包括正常发育、成人组织动态平衡的维持以及肿瘤的发生过程。这项工作的总体目标是揭示T3对肠道上皮细胞分化产生深刻影响的分子机制。T3作用的最初模式包括它与受体蛋白(Tr)的结合，然后受体蛋白在被称为甲状腺反应元件(Tre)的位置与靶基因相互作用，导致转录速率的正或负变化。然而，在过去的几年里，模式发生了转变，现在已知T3的作用涉及到各种其他蛋白质(共激活蛋白和共抑制蛋白)。此外，T3-TR与DNA的相互作用受到染色质结构(组蛋白)的高度调控。这项研究计划旨在阐明T3介导的对肠上皮细胞的影响所依赖的复杂的分子相互作用。在以前的工作中，甲状腺激素被证明可以不同地调节肠道基因的转录，增加肠道碱性磷酸酶(IAP)和降低乳糖酶的表达。在特定的目标#1中，将使用两种新的方法来研究T3改变这两个靶基因的机制，即稳定报告分析和染色质免疫沉淀(ChIP)分析。之所以选择这两种方法，是因为它们在内源性染色质的背景下提供了关于转录事件的信息，而不是过去分子研究中使用的裸DNA。在特定的目标#2中，将进一步利用稳定的报告分析来阐明组蛋白修饰在肠道内T3介导的转录事件中所起的作用。我们将检查诱导组蛋白超乙酰化的试剂(短链脂肪酸)，以及一系列脱乙酰化组蛋白的酶(HDAC1、2和3)。最后，在具体目标#3中，将研究两种潜在的肠道内T3作用的内源性抑制物。CD1对T3作用的抑制可能是其基本的“抗分化”作用的基础，也可能与其在结肠癌发生中的作用有关。非受体troc-2的T3抑制作用可能是在各种疾病状态下发生的肠道粘膜功能障碍的基础，包括长期饥饿和严重创伤。人们希望，对控制肠道内T3作用的分子事件的阐明将提供潜在的治疗靶点，这些靶点可以被操纵以在病理条件下维持肠粘膜的完整性。表演网站========================================Section End===========================================

EXCEED THE SPACE PROVIDED. Thyroid Hormone (T3) is one of the most potent regulators of intestinalepithelialstructure and function. T3 appears to play a vital role in virtually all aspects of gut epithelial biology, including normal development, maintenance of tissue homeostasis in the adult, as well as the process of neoplasia. The overall goals of this work are to unravel the molecular mechanisms by which T3 exerts its profound effects on gut epithelialdifferentiation. The initial model of T3 action involved its binding to a receptor protein (TR) which then interacted with target genes at sites called thyroid response elements (TRE), resulting in either positive or negative changes in transcriptional rates. Over the past several years, however, a paradigm shift has occurred such that T3 action is now known to involve a variety of other proteins (co-activators and co-repressors). Furthermore, the T3-TR interaction with DNA is highly regulated by the chromatin structure (histones). This research proposal is designed to elucidate the complex molecular interactions that underlie the T3-mediated effects on intestinal epithelia. In previous work, thyroid hormone has been shown to differentially regulate gut gene transcription, increasing intestinal alkalinephosphatase (IAP) and decreasing lactase expression. In Specific Aim #1, the mechanism by which T3 alters these two target genes will be examined by using two novel approaches, stable reporter assays and the chromatin immuno-precipitation (ChIP) assay. These two approaches have been chosen specifically because they provide information regarding transcriptional events in the context of endogenous chromatin, rather than the naked DNA used in past molecular studies. In Specific Aim #2, the stable reporter assays will be further utilized in order to elucidate the role that histone modification plays in T3-mediated transcriptionalevents within the gut. We will examine agents that induce histone hyperacetylation (short chain fatty acids), as well as a family of enzymes that deacetylate histones (HDAC 1, 2, and 3). Finally, in Specific Aim #3, two potential endogenous inhibitors of T3 action within the gut will be studied. The cyclin Dl (CD1) inhibition of T3 action may underlie its fundamental "anti-differentiating" effects, as well as being related to its role in colon carcinogenesis. The T3 inhibitory effects of the non-receptor, TRoc-2, may underliethe gut mucosal dysfunction that occurs in a variety of disease states, including prolonged starvation and severe trauma. It is hoped that an elucidation of the molecular events that govern T3 action within the gut will provide potential therapeutic targets that could be manipulated to maintain the integrity of the intestinalmucosa under pathologic conditions. PERFORMANCE SITE ========================================Section End===========================================