REGULATION OF TRH GENE EXPRESSION IN NEUROENDOCRINE CELL

促甲状腺激素释放激素(TRH)在 大鼠下丘脑对促甲状腺激素(TSH)分泌的调节 垂体前叶广泛分布于下丘脑外 神经内分泌组织。尽管这种神经肽在体内起着关键作用 神经元和内分泌系统之间的信息传递，很少 已知调节TRH基因表达的因素。 DNA序列的鉴定及反式作用因子基因的克隆 调节TRH基因的表达将提供大量的洞察力 神经肽类激素在正常和异位中表达机制的探讨 分泌激素的神经内分泌细胞。 这个提议的主要目的是1)识别顺式作用的dna。 决定TRH基因组织特异性表达的序列，2) 鉴定与TRH序列结合的反式作用因子(S) 对基因表达很重要，3)分离并测序编码 TRH反式作用因子。我的初步结果表明，TRH -47~-113bp之间的片段对TRH基因的表达具有重要意义。 在这个片段中有两个与组织同源的序列- 生长抑素基因的特异性/cAMP增强子(TSE/Cre)。的研究 元素及其周围的核苷酸表明它们可以作为 增强子元件，并受DNA酶核提取液中的因子保护 我的足迹分析。足迹分析与竞争研究 证明TRH-蛋白质复合体可以与 SS启动子元件的TRH。共享的序列同源性 由神经肽基因TRH和SS提示，这些同源基因 元素可能是共享的反式作用因子的结合位点 不同的神经内分泌细胞和异位神经肽分泌肿瘤。 分泌TRH和SS的甲状腺髓样癌细胞系CA77 提供了一个理想的模型来检验单个交易的理论 因子可以调节这两种神经肽基因的表达。 阐明其潜在的细胞和分子机制 TRH基因的表达将增加我们对控制的理解 大脑对垂体-甲状腺轴的影响及其分子基础 神经内分泌细胞中多肽激素的表达。

Thyrotropin releasing hormone (TRH) plays a pivotal role in the hypothalamic regulation of thyroid stimulating hormone (TSH) secretion from the anterior pituitary and is widely distributed in extrahypothalamic neuroendocrine tissues. Although this neuropeptide plays a key role in the transduction of information between neuronal and endocrine systems, little is known about the factors that regulate TRH gene expression. Identification of the DNA sequence and cloning the trans-acting factor cDNA that regulates TRH gene expression would provide a great deal of insight into the mechanism of neuropeptide hormone expression in normal and ectopic hormone secreting neuroendocrine cells. The major aims of this proposal are to 1) identify the cis-acting DNA sequences that determine tissue-specific expression of the TRH gene, 2) characterize the trans-acting factor(s) that bind to the TRH sequences important for gene expression, 3) isolate and sequence a cDNA encoding the TRH trans-acting factor. My preliminary results demonstrate that the TRH fragment between -47 and -113 bp is important for TRH gene expression. Within this fragment are two sequences that are homologous to the tissue- specific/cAMP enhancer (TSE/CRE) of the somatostatin (SS) gene. Studies of the elements with its surrounding nucleotides suggest they can function as enhancer elements and are protected by factors in nuclear extracts in DNase I footprinting assays. Footprinting assays with competition studies demonstrate that the TRH-protein complex can be dissociated equally with either the TRH of the SS promoter element. The sequence homologies shared by the neuropeptide genes, TRH and SS, suggest that these homologous elements might be binding sites for trans-acting factors shared by different neuroendocrine cells and ectopic neuropeptide secreting tumors. The TRH and SS secreting medullary thyroid carcinoma cell line, CA77, provides and ideal model to test the theory that a single trans-acting factor can regulate the expression of both neuropeptide genes. Elucidation of the cellular and molecular mechanisms underlying the expression of the TRH gene will increase our understanding of the control of the pituitary-thyroid axis by the brain and the molecular basis of peptide hormone expression in neuroendocrine cells.