Structural understanding of 7SK-snRNP mediated transcriptional regulation

摘要 在许多细胞和病毒mRNAs的转录过程中，RNA聚合酶II被抑制 负的伸长系数，需要正的伸长系数pTEFb才能释放 停滞状态。7SK小核RNA与HEXIM接头蛋白的部分结合 在7SK小核糖核蛋白(7SK SnRNP)复合体中，通常保持pTEFb 隔离在原子核内，这种相互作用必须克服，才能产生成效 转录延伸。对监管机制研究最充分的例子是 转录延长的基础是HIV TAT系统。简而言之，为了释放停滞不前的 在转录状态下，HIV已经进化出病毒Tat蛋白，它与7SK结合并取代 HEXIM要劫持pTEFb。另一方面，一些细胞因子，如BRD4，也能达到同样的效果 结果不会取代HEXIM。这项建议的目的是机械性地理解 结构状态呈现给所有遇到HEXIM驱动的转录调控因子 抑制性7SK SnRNP复合体，以及特殊的HIV如何实现对pTEFb的捕获 TAT转录因子。目标将是：(#1)了解基本机制是否 在HEXIM1和2中保持，如果不同的正转录调控因子利用 机制，(#2)，以确定7SK-中存在的单个RNA结构域的结构 SnRNA和(#3)来求解HEXIM结合和TAT结合的络合物的结构。

Abstract During transcription of many cellular and viral mRNAs, RNA Polymerase II is inhibited by negative elongation factors and requires the positive elongation factor, pTEFb, to release this stalled state. The binding of the 7SK small nuclear RNA to the HEXIM adapter protein as a part of the 7SK small nuclear ribonucleoprotein (7SK snRNP) complex normally keeps pTEFb sequestered within the nucleus and this interaction must be overcome for productive transcriptional elongation. The most well-studied example of the regulatory mechanisms that underlie transcriptional elongation is the HIV Tat system. Briefly, in order to release the stalled state of its transcript, HIV has evolved the viral Tat protein, which binds 7SK and displaces HEXIM to hijack pTEFb. On the other hand, some cellular factors, like BRD4, achieve the same outcome without displacing HEXIM. This proposal aims to gain a mechanistic understanding of the structural state presented to all transcriptional regulators encountering an HEXIM-driven inhibitory 7SK snRNP complex, and how capture of pTEFb is achieved by the specialized HIV Tat transcriptional factor. The aims will be: (#1) to understand if the basic mechanisms are maintained in HEXIM1 and 2 and if diverse positive transcriptional regulators capitalize on the mechanism, (#2) to determine the structures of the individual RNA domains present in 7SK- snRNA and (#3) to solve the structures of both HEXIM-bound and Tat-bound complexes.