Regulation of polymerase II transcription by 7SK snRNA: Two distinct RNA elements direct P-TEFb and HEXIM1 binding
Regulation of polymerase II transcription by 7SK snRNA: Two distinct RNA elements direct P-TEFb and HEXIM1 binding
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DOI：
10.1128/mcb.26.2.630-642.2006
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发表时间：
2006-01-01
影响因子：
5.3
通讯作者：
Kiss, T
中科院分区：
文献类型：
--
作者：
Egloff, S;Van Herreweghe, E;Kiss, T
正转录延伸因子b （P-TEFb）是Cdk9和细胞周期蛋白T1/T2的复合物，通过磷酸化RNA聚合酶h来刺激转录。7SK小核RNA与HEXIM1蛋白合作，通过将P-TEFb分离到一个大型激酶无活性的7SK/HEXIM1/P-TEFb复合物中，作为一般的聚合酶II转录调节因子。在这里，对人类7SK snRNA中指导HEXIM1和P-TEFb结合的功能必需元件的测定和表征导致了7SK/HEX1M1/P-TEFb调控复合物组装的新模型。我们证明了位于7SK 5‘和3’末端发夹上的两个结构和功能不同的蛋白质结合元件支持HEXIM1和P-TEFb的体内募集。一致地，由7SK的5‘和3’发夹组成的最小调节RNA可以调节HeLa细胞中聚合酶II的转录。HEXIM1独立特异性结合到7SK 5'发卡的G24-C48/G60-C87远端。HEXIM1的结合是P-TEFb与7SK 3'发卡的G302-C324顶端区域关联的先决条件，这与人类免疫缺陷病毒反应性RNA高度相似。
The positive transcription elongation factor b (P-TEFb), a complex of Cdk9 and cyclin T1/T2, stimulates transcription by phosphorylating RNA polymerase H. The 7SK small nuclear RNA, in cooperation with HEXIM1 protein, functions as a general polymerase II transcription regulator by sequestering P-TEFb into a large kinase-inactive 7SK/HEXIM1/P-TEFb complex. Here, determination and characterization of the functionally essential elements of human 7SK snRNA directing HEXIM1 and P-TEFb binding led to a new model for the assembly of the 7SK/HEX1M1/P-TEFb regulatory complex. We demonstrate that two structurally and functionally distinct protein binding elements located in the 5'- and 3'-terminal hairpins of 7SK support the in vivo recruitment of HEXIM1 and P-TEFb. Consistently, a minimal regulatory RNA composed of the 5' and 3' hairpins of 7SK can modulate polymerase II transcription in HeLa cells. HEXIM1 binds independently and specifically to the G24-C48/G60-C87 distal segment of the 5' hairpin of 7SK. Binding of HEXIM1 is a prerequisite for association of P-TEFb with the G302-C324 apical region of the 3' hairpin of 7SK that is highly reminiscent of the human immunodeficiency virus transactivation-responsive RNA.