一种人源细胞周期蛋白 T1 突变体的功能特征揭示了其与 Tat 和 HEXIM1 的不同结合表面。

Functional characterization of a human cyclin T1 mutant reveals a different binding surface for Tat and HEXIM1.

机构信息

Department of Virology and Developmental Genetics Faculty of Health Sciences, Ben-Gurion University of the Negev, Israel.

出版信息

Virology. 2012 May 10;426(2):152-61. doi: 10.1016/j.virol.2012.01.033. Epub 2012 Feb 18.

DOI:10.1016/j.virol.2012.01.033

PMID:22342181

Abstract

HIV transcription is regulated at the step of elongation by the viral Tat protein and the cellular positive transcription elongation factor b (P-TEFb; Cdk9/cyclin T1). Herein, a human cyclin T1 mutant, cyclin T1-U7, which contains four substitutions and one deletion in the N-terminal cyclin box, was stably expressed in HeLa cells. HIV transcription was efficiently inhibited in HeLa-HA-CycT1-U7 stable cells. Cyclin T1-U7 bound Tat but did not modulate its expression levels, which remained high. Importantly cyclin T1-U7 failed to interact with Cdk9 or HEXIM1 and did not interfere with endogenous P-TEFb activity to stimulate MEF2C or NFkB mediated transcription. In a T cell line and primary CD4+ cells, cyclin T1-U7 also inhibited HIV transcription. We conclude that cyclin T1-U7 sequesters Tat from P-TEFb and inhibits HIV transcription. Importantly, N-terminal residues in cyclin T1 are specifically involved in the binding of cyclin T1 to HEXIM1 but not to Tat.

摘要

HIV 的转录在延伸步骤受病毒 Tat 蛋白和细胞正转录延伸因子 b（P-TEFb；Cdk9/ 周期蛋白 T1）调控。在此，稳定表达于 HeLa 细胞中的人 cyclin T1 突变体 cyclin T1-U7 在 N 端 cyclin 框中含有四个取代和一个缺失。HIV 转录在 HeLa-HA-CycT1-U7 稳定细胞中被有效抑制。cyclin T1-U7 与 Tat 结合，但不调节其表达水平，Tat 的表达水平仍然很高。重要的是，cyclin T1-U7 不能与 Cdk9 或 HEXIM1 相互作用，也不干扰内源性 P-TEFb 活性来刺激 MEF2C 或 NFkB 介导的转录。在 T 细胞系和原代 CD4+细胞中，cyclin T1-U7 也抑制 HIV 转录。我们的结论是，cyclin T1-U7 将 Tat 与 P-TEFb 隔离并抑制 HIV 转录。重要的是，cyclin T1 的 N 端残基特异性地参与 cyclin T1 与 HEXIM1 的结合，但不与 Tat 结合。