The bromodomain protein Brd4 is a positive regulatory component of P-TEFb and stimulates RNA polymerase II-dependent transcription
The bromodomain protein Brd4 is a positive regulatory component of P-TEFb and stimulates RNA polymerase II-dependent transcription
复制标题
DOI：
10.1016/j.molcel.2005.06.027
复制
发表时间：
2005-08-19
期刊：
影响因子：
16
通讯作者：
Ozato, K
中科院分区：
文献类型：
--
作者：
Jang, MK;Mochizuki, K;Ozato, K
Brd4 是一种哺乳动物溴结构域蛋白，可与乙酰化染色质结合。蛋白质组学分析表明，Brd4 与 cyclinT1 和 Cdk9 相互作用，构成核心正转录延伸因子 b (P-TEFb)。 Brd4 通过其溴结构域与活核中的 P-TEFb 相互作用。大约一半的 P-TEFb 与抑制亚基结合并且功能失活。 Brd4 与不含抑制亚基的 P-TEFb 相互作用。 Brd4 表达的增加导致 RNA 聚合酶 II (RNAPII) CTD 的 P-TEFb 依赖性磷酸化增加，并刺激体内启动子的转录。相反，通过 siRNA 减少 Brd4 表达会降低 CTD 磷酸化和转录，表明 Brd4 是 P-TEFb 的正调控成分。在染色质免疫沉淀 (ChIP) 测定中，P-TEFb 向启动子的募集依赖于 Brd4，并通过染色质乙酰化的增加而增强。 P-TEFb 与 Brd4 和抑制亚基一起交替相互作用，以维持细胞内的功能平衡。
Brd4 is a mammalian bromodomain protein that binds to acetylated chromatin. Proteomic analysis revealed that Brd4 interacts with cyclinT1 and Cdk9 that constitutes core positive transcription elongation factor b (P-TEFb). Brd4 interacted with P-TEFb in the living nucleus through its bromodomain. About half of P-TEFb was bound to the inhibitory subunit and functionally inactive. Brd4 interacted with P-TEFb that was free of the inhibitory subunit. An increase in Brd4 expression led to increased P-TEFb-dependent phosphorylation of RNA polymerase II (RNAPII) CTD and stimulation of transcription from promoters in vivo. Conversely, a reduction in Brd4 expression by siRNA reduced CTD phosphorylation and transcription, revealing that Brd4 is a positive regulatory component of P-TEFb. In chromatin immunoprecipitation (ChIP) assays, the recruitment of P-TEFb to a promoter was dependent on Brd4 and was enhanced by an increase in chromatin acetylation. Together, P-TEFb alternately interacts with Brd4 and the inhibitory subunit to maintain functional equilibrium in the cell.