Marshall N F, Peng J, Xie Z, Price D H
Department of Biochemistry, University of Iowa, Iowa City, Iowa 52242, USA.
J Biol Chem. 1996 Oct 25;271(43):27176-83. doi: 10.1074/jbc.271.43.27176.
The entry of RNA polymerase II into a productive mode of elongation is controlled, in part, by the postinitiation activity of positive transcription elongation factor b (P-TEFb) (Marshall, N. F., and Price, D. H. (1995) J. Biol. Chem. 270, 12335-12338). We report here that removal of the carboxyl-terminal domain (CTD) of the large subunit of RNA polymerase II abolishes productive elongation. Correspondingly, we found that P-TEFb can phosphorylate the CTD of pure RNA polymerase II. Furthermore, P-TEFb can phosphorylate the CTD of RNA polymerase II when the polymerase is in an early elongation complex. Both the function and kinase activity of P-TEFb are blocked by the drugs 5, 6-dichloro-1-beta-D-ribofuranosylbenzimidazole (DRB) and H-8. P-TEFb is distinct from transcription factor IIH (TFIIH) because the two factors have no subunits in common, P-TEFb is more sensitive to DRB than is TFIIH, and most importantly, TFIIH cannot substitute functionally for P-TEFb. We propose that phosphorylation of the CTD by P-TEFb controls the transition from abortive into productive elongation mode.
RNA聚合酶II进入高效延伸模式部分受正性转录延伸因子b（P-TEFb）起始后活性的控制（Marshall, N. F., and Price, D. H. (1995) J. Biol. Chem. 270, 12335 - 12338）。我们在此报告，去除RNA聚合酶II大亚基的羧基末端结构域（CTD）会消除高效延伸。相应地，我们发现P-TEFb可磷酸化纯RNA聚合酶II的CTD。此外，当聚合酶处于早期延伸复合物中时，P-TEFb可磷酸化RNA聚合酶II的CTD。P-TEFb的功能和激酶活性均被5,6-二氯-1-β-D-呋喃核糖基苯并咪唑（DRB）和H-8阻断。P-TEFb与转录因子IIH（TFIIH）不同，因为这两个因子没有共同的亚基，P-TEFb比TFIIH对DRB更敏感，且最重要的是，TFIIH在功能上不能替代P-TEFb。我们提出，P-TEFb对CTD的磷酸化控制着从无效延伸到高效延伸模式的转变。
