BIOCHEMICAL MECHANISM OF TRANS-ACTIVATION IN HTLV-I

人类嗜T淋巴细胞逆转录病毒I型(HTLV-I)是一种 编码调节基因的一组逆转录病毒(HTLV-I、HTLV-II、STLV、BLV) 调节病毒信使核糖核酸合成和利用的蛋白质。40 kDa 核蛋白Tax是由HTLV-I基因组3‘端编码的一种核蛋白。 转录激活剂。税收改变基因表达的能力 在HTLV-I感染细胞中似乎与HTLV-I有因果关系 发病机制。 TAX激活U3区三个21bp重复序列的转录 病毒长末端重复序列(LTR)。它还能激活转录 来自含有核因子-kB结合位点的增强子/启动子。饱和 21个碱基重复序列的突变表明，介导 税收反应存在于与阵营反应同源的TGACGT基序中 元件(Cre)存在于许多生物的转录调控区域 病毒和细胞基因。 过去两年的研究努力达到了顶峰 CAMP反应元件结合蛋白CREB的鉴定 税收的主要目标。通过蛋白质-蛋白质相互作用，Tax 与CREB形成复合体并增强其与HTLV-I 21bp的结合 重复着。此外，CREB既以同源二聚体形式存在，又以杂二聚体形式存在 在与不同的Cre结合蛋白的复合体中，暂定称为Caf (CREB相关因子)。CREB同源二聚体和CREB/CaF杂二聚体 与税收互动。这些发现为下一步研究提供了基础 税收行为的机制。 这一建议试图阐明蛋白质-蛋白质和蛋白质-DNA 通过HTLV-I Tax介导转录激活的相互作用。 将特别强调使用提纯的组件 包括TAX、CREB、CAF和基础转录因子 剖析了税收行为的机制。试剂和实验 为HTLV-I税开发的方法将扩展到以下研究 牛白血病病毒税务蛋白。最后，税收机制 还将检查核因子-kB结合位点的激活情况。

Human T-lymphotropic retrovirus type I (HTLV-I) is the prototype of a group of retroviruses (HTLV-I, HTLV-II, STLV, BLV) that encode regulatory proteins to modulate viral mRNA synthesis and utilization. The 40 kDa nuclear protein, Tax, encoded by the 3' region of HTLV-I genome is a transcriptional activator. The ability of tax to alter gene expression in HTLV-I infected cells appears to be causally related to HTLV-I pathogenesis. Tax activates transcription from three 21 bp repeats in the U3 region of the viral long terminal repeat (LTR). It also activates transcription from enhancer/promoters containing the NF-kB binding sites. Saturation mutagenesis of the 21 bp repeat indicates that the key element mediating tax response lies in a TGACGT motif homologous to the cAMP responsive element (CRE) found in the transcriptional regulatory region of many viral and cellular genes. Research efforts over the past two years have culminated in the identification of cAMP responsive element binding protein, CREB, as one of the primary targets of tax. Via protein-protein interaction, Tax forms a complex with CREB and enhances its binding to the HTLV-I 21 bp repeats. Furthermore, CREB exists both as a homodimer and a heterodimer in complex with a distinct CRE binding protein tentatively called CAF (CREB associated factor). Both CREB homodimer and CREB/CAF heterodimer interact with Tax. These findings provide the foundation for studying the mechanism of tax action. This proposal seeks to elucidate the protein-protein and protein-DNA interactions that mediate transcriptional activation by HTLV-I tax. Special emphasis will be directed towards using purified components including Tax, CREB, CAF, and the basal transcriptional factors to dissect the mechanism of Tax action. The reagents and experimental approaches developed for HTLV-I Tax will then be extended to the study of bovine leukemia virus Tax protein. Finally, the mechanism of tax activation from NF-kB binding sites will also be examined.