Regulation of P-TEFb elongation complex activity by CDK9 acetylation
Regulation of P-TEFb elongation complex activity by CDK9 acetylation
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DOI：
10.1128/mcb.00857-06
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发表时间：
2007-07-01
影响因子：
5.3
通讯作者：
Wong, Jiemin
中科院分区：
文献类型：
--
作者：
Fu, Junjiang;Yoon, Ho-Geun;Wong, Jiemin
P-TEFb由CDK9和细胞周期蛋白T亚基组成，是一种对大多数RNA聚合酶II(PolII)转录起重要作用的全局性转录延伸因子。P-TEFb通过磷酸化PolII最大亚基的羧基末端结构域(CTD)的七肽重复序列Ser2来促进转录延长。先前的研究表明，P-TEFb通过与7SK小RNA和HEXIM1形成一个非活性的复合体而受到负调控。为了研究辅阻遏子N-cor介导转录抑制的分子机制，我们将HEXIM1鉴定为N-cor相互作用蛋白。这一发现促使我们测试P-TEFb复合体是否受乙酰化的调节。我们证明CDK9在细胞中是一种乙酰化的蛋白质，并且在体外可以被p300乙酰化。通过体外和体内实验，我们确定CDK9的赖氨酸44是主要的乙酰化位点。我们发现CDK9受N-COR及其相关的HDAC3的调节，并且CDK9的乙酰化影响其磷酸化PolII的CTD的能力。这些结果表明CDK9的乙酰化是一个重要的翻译后修饰，参与调节P-TEFb的转录延伸功能。
P-TEFb, comprised of CDK9 and a cyclin T subunit, is a global transcriptional elongation factor important for most RNA polymerase II (pol II) transcription. P-TEFb facilitates transcription elongation in part by phosphorylating Ser2 of the heptapeptide repeat of the carboxy-terminal domain (CTD) of the largest subunit of pol II. Previous studies have shown that P-TEFb is subjected to negative regulation by forming an inactive complex with 7SK small RNA and HEXIM1. In an effort to investigate the molecular mechanism by which corepressor N-CoR mediates transcription repression, we identified HEXIMl as an N-CoR-interacting protein. This finding led us to test whether the P-TEFb complex is regulated by acetylation. We demonstrate that CDK9 is an acetylated protein in cells and can be acetylated by p300 in vitro. Through both in vitro and in vivo assays, we identified lysine 44 of CDK9 as a major acetylation site. We present evidence that CDK9 is regulated by N-CoR and its associated HDAC3 and that acetylation of CDK9 affects its ability to phosphorylate the CTD of pol II. These results suggest that acetylation of CDK9 is an important posttranslational modification that is involved in regulating P-TEFb transcriptional elongation function.