Shiekhattar R, Mermelstein F, Fisher R P, Drapkin R, Dynlacht B, Wessling H C, Morgan D O, Reinberg D
Howard Hughes Medical Institute, Department of Biochemistry, Robert Wood Johnson Medical School, University of Medicine and Dentistry of New Jersey, Piscataway 08854-5635.
Nature. 1995 Mar 16;374(6519):283-7. doi: 10.1038/374283a0.
Transcription factor IIH (TFIIH) contains a kinase capable of phosphorylating the carboxy-terminal domain (CTD) of the largest subunit of RNA polymerase II (RNAPII). Here we report the identification of the Cdk-activating kinase (Cak) complex (Cdk7 and cyclin H) as a component of TFIIH after extensive purification of TFIIH by chromatography. We find that affinity-purified antibodies directed against cyclin H inhibit TFIIH-dependent transcription and that both cyclin H and Cdk7 antibodies inhibit phosphorylation of the CTD of the largest subunit of the RNAPII in the preinitiation complex. Cak is present in at least two distinct complexes, TFIIH and a smaller complex that is unable to phosphorylate RNAPII in the preinitiation complex. Both Cak complexes, as well as recombinant Cak, phosphorylate a CTD peptide. Finally, TFIIH was shown to phosphorylate both Cdc2 and Cdk2, suggesting that there could be a link between transcription and the cell cycle machinery.
转录因子IIH（TFIIH）含有一种激酶，能够磷酸化RNA聚合酶II（RNAPII）最大亚基的羧基末端结构域（CTD）。在此，我们报告在通过色谱法对TFIIH进行广泛纯化后，鉴定出细胞周期蛋白依赖性激酶激活激酶（Cak）复合物（Cdk7和细胞周期蛋白H）是TFIIH的一个组成部分。我们发现，针对细胞周期蛋白H的亲和纯化抗体可抑制TFIIH依赖性转录，并且细胞周期蛋白H抗体和Cdk7抗体均能抑制起始前复合物中RNAPII最大亚基CTD的磷酸化。Cak存在于至少两种不同的复合物中，即TFIIH和一种较小的复合物，后者在起始前复合物中无法磷酸化RNAPII。两种Cak复合物以及重组Cak均可磷酸化CTD肽段。最后，研究表明TFIIH可磷酸化Cdc2和Cdk2，这表明转录与细胞周期机制之间可能存在联系。
