REGULATION OF CBP/P300 IN NUCLEAR RECEPTOR FUNCTION

类固醇激素和维生素，包括糖皮质激素和维生素A衍生物，通过直接调节基因转录而诱导细胞分化，并经常与抑制细胞生长有关。核受体与激素和维生素结合，通过招募乙酰酶共激活复合体来激活激素反应基因。这项建议的长期目标是：(A)破译涉及受体和辅激活子功能的新的调节机制；(B)确定受体共激活复合体的新成分；以及(C)剖析将激素信号转化为转录和生理反应的复合体的调节特性。为了实现上述目标，将追求以下具体目标：(1)检验CBP/p300的两个核受体相互作用结构域对于核受体介导的基因激活是必需的假设。(Ii)确定CBP/p300的组蛋白乙酰转移酶(HAT)相关结构域在转录激活中的作用，并检验HAT介导的反式激活需要额外蛋白质的假设。(Iii)验证腺病毒癌蛋白E1a的恒定区2(CR2)和恒定区3(CR3)作为HAT抑制结构域的假设，并确定E1A抑制转录的机制。酵母双杂交筛选将用于鉴定和鉴定新的CBP/p300调节蛋白。这些研究具有重要的临床意义，因为：(A)核受体激动剂和拮抗剂在治疗乳腺癌、前列腺癌、白血病、糖尿病和心血管疾病方面有用；(B)核受体及其辅助因子的染色体易位和扩增与白血病和乳腺癌有关，提示受体或其辅助激活物的异常靶向或活性调节可能在白血病和肿瘤的发生中发挥重要作用。上述旨在实现长期目标的具体目标的实现，应有助于更好地了解核受体和辅活化子在转录和包括癌症在内的人类疾病中的作用。

Steroid hormones and vitamins including glucocorticoids and vitamin A derivatives act to induce cellular differentiation by directly modulating gene transcription and are often associated with the inhibition of cell growth. Nuclear receptors bind to hormones and vitamins and activate hormone responsive genes by recruiting an acetylase co-activation complex. The broad long- term objectives of this proposal are: (a) to decipher novel regulatory mechanisms involved in receptor and coactivator function; (b) to identify new components of the receptor coactivation-complex; and (c) to dissect the regulatory properties of the complex that translate a hormonal signal into transcriptional and physiological responses. To achieve the above goals, the following Specific Aims will be pursued: (I) To test the hypothesis that both nuclear receptor interaction domains of CBP/p300 are necessary for nuclear receptor mediated gene activation. (II) To determine the roles of the histone acetyltransferase (HAT)- associated domains of CBP/p300 in transcriptional activation and to test the hypothesis that additional proteins are necessary for HAT-mediated transactivation. (III) To test the hypothesis that constant region 2 (CR2) and constant region 3 (CR3) of adenoviral oncoprotein E1A function as the HAT-inhibitory domains and to determine the mechanism of transcription inhibition by E 1 A. A combination of in vitro binding, site directed mutagenesis, deletion analysis, and mammalian cell transfection based in vivo assays will be utilized to address the above Specific Aims. Yeast two-hybrid screens will be employed to identify and characterize novel CBP/p300 regulatory proteins. These studies are clinically significant because: (a) nuclear receptor agonists and antagonists are useful in treatment of breast, and prostate cancer, leukemia, diabetes, and cardiovascular diseases; and (b) chromosomal translocations and amplification of nuclear receptors and their cofactors have been implicated in leukemia and breast cancer suggesting abnormal targeting or regulation of the activities of receptors or their coactivators may play important roles in leukemia and oncogenesis. The accomplishment of the Specific Aims described above geared towards achieving the long- term goals should provide a better understanding of the role of nuclear receptors and coactivators in transcription and in human diseases including cancer.