Molecular mechanism of transactivation via transcriptional coactivator complexes

通过转录共激活因子复合物反式激活的分子机制

基本信息

批准号：
12480206
负责人：
NAKAJIMA Toshihiro
金额：
$ 6.34万
依托单位：
St. Marianna University School of Medicine
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2000
资助国家：
日本
起止时间：
2000 至 2002
项目状态：
已结题

项目摘要

In the eukaryotic gene expression, recruitment of the basal transcriptional machinery including RNA polymerase (Pol) II is a principle mechanism for transcriptional activation. A specific transcriptional factor interacts with components of this machinery and localizes them to a specific promoter. For example, cAMP responsive element binding protein (CREB) stimulates target gene expression by recruitment of CREB binding protein (CBP). CBP interacting phosphorylated CREB activates the transcription via two mechanisms. One is dependent on the histone acetyltransferase activity (HAT), another is recruitment of Pol II mediated by RNA helicase A (RHA). RHA is a member of the DExH family of ATPases / helicases and catalyzes the displacement of both double-stranded RNA and DNA from 3' to 5'. We found that RHA recruits Pol II to breast cancer specific tumor suppressor protein (BRCA1) and enhance HIV virus gene expression.For further an understanding of the role of RHA on gene expression, we have identified a 50 amino acid transactivation domain that interacts with Pol II and termed it the minimal transactivation domain (MTAD) in this project. The protein sequence of this region contains six hydrophobic residues and is unique to RHA homologues and well conserved. A mutant with this region deleted from full-length RHA decreased transcriptional activity in CREB-dependent transcription. In addition, mutational analyses revealed that several tryptophan residues in MTAD are important for the interaction with Pol II and transactivation. These results suggest that RHA could independently regulate CREB-dependent transcription either through recruitment of Pol II or ATP dependent mechanisms.

在真核基因的表达中，包括RNA聚合酶（POL）II的基础转录机械的募集是转录激活的主要机制。特定的转录因子与该机械的组件相互作用，并将其定位到特定的启动子。例如，cAMP响应元件结合蛋白（CREB）通过募集CREB结合蛋白（CBP）刺激靶基因表达。 CBP相互作用的磷酸化CREB通过两种机制激活转录。一种取决于组蛋白乙酰转移酶活性（HAT），另一个是由RNA解旋酶A（RHA）介导的POL II的募集。 RHA是ATPases / Helicases的DexH家族的成员，并催化双链RNA和DNA的位移从3'至5'。我们发现RHA将POL II招募到乳腺癌特异性肿瘤抑制蛋白（BRCA1）并增强HIV病毒基因表达。为了进一步了解RHA在基因表达中的作用，我们已经确定了与POL相互作用的50个氨基酸反式激活结构II并将其称为该项目中最小的反式激活域（MTAD）。该区域的蛋白质序列包含六个疏水残基，并且是RHA同源物独有的，并且保守了。从全长RHA中删除该区域的突变体在CREB依赖性转录中降低了转录活性。此外，突变分析表明，MTAD中的一些色氨酸残基对于与POL II和反式激活的相互作用很重要。这些结果表明，RHA可以通过募集POL II或依赖ATP的机制独立调节CREB依赖性转录。