PDF(Pubmed)
Abstract：
The BET family protein BRD4, which forms the CDK9-containing BRD4-PTEFb complex, is considered to be a master regulator of RNA polymerase II (Pol II) pause release. Because its tandem bromodomains interact with acetylated histone lysine residues, it has long been thought that BRD4 requires these bromodomains for its recruitment to chromatin and transcriptional regulatory function. Here, using rapid depletion and genetic complementation with domain deletion mutants, we demonstrate that BRD4 bromodomains are dispensable for Pol II pause release. A minimal, bromodomain-less C-terminal BRD4 fragment containing the PTEFb-interacting C-terminal motif (CTM) is instead both necessary and sufficient to mediate Pol II pause release in the absence of full-length BRD4. Although BRD4-PTEFb can associate with chromatin through acetyl recognition, our results indicate that a distinct, active BRD4-PTEFb population functions to regulate transcription independently of bromodomain-mediated chromatin association. These findings may enable more effective pharmaceutical modulation of BRD4-PTEFb activity.
摘要：
BET家族蛋白BRD4，形成含CDK9的BRD4-PTEFb复合物，被认为是RNA聚合酶II(PolII)暂停释放的主要调节因子。因为它的串联溴结构域与乙酰化组蛋白赖氨酸残基相互作用，长期以来，人们一直认为BRD4需要这些溴结构域来招募染色质和转录调节功能。这里,使用快速耗竭和结构域缺失突变体的遗传互补，我们证明BRD4溴结构域对于PolII暂停释放是不必要的。一个最小的，相反，含有PTEFb相互作用的C末端基序（CTM）的无溴结构域C末端BRD4片段对于在不存在全长BRD4的情况下介导PolII暂停释放既必要又足够。虽然BRD4-PTEFb可以通过乙酰基识别与染色质结合，我们的结果表明，一个独特的，活性BRD4-PTEFb群体的功能是独立于溴结构域介导的染色质关联调节转录。这些发现可以实现BRD4-PTEFb活性的更有效的药物调节。
