Transcription-dependent association of multiple positive transcription elongation factor units to a HEXIM multimer
Transcription-dependent association of multiple positive transcription elongation factor units to a HEXIM multimer
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DOI：
10.1074/jbc.m502471200
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发表时间：
2005-08-26
影响因子：
4.8
通讯作者：
Bensaude, O
中科院分区：
文献类型：
--
作者：
Dulac, C;Michels, AA;Bensaude, O
阳性转录延伸因子(P-TEFb)包括一个K、CDK9和一个Cyclin T1或T2。它的活性被与7SK小核RNA结合的HEXIM1或HEXIM2蛋白所抑制。HEXIM1和HEXIM2形成稳定的同源和杂相齐聚物。利用酵母双杂交和转染法，我们现在已经证明HEXIM蛋白的C-末端结构域直接相互作用。甘油梯度超速离心法和凝胶渗透层析法测定的流体力学参数表明，纯化的重组和细胞HEXIM1蛋白都形成了高度各向异性的颗粒。化学交联表明HEXIM1蛋白形成二聚体。HEXIM1的多聚体性质在P-TEFb(.)HEXIM1(.)7SK RNA复合物中保持不变。在不活跃的P-TEFb(.)HEXIM1(.)7SK络合物中发现了多个P-TEFb模块。有人认为，7SK RNA与HEXIM1多聚体结合促进了多个P-TEFb单位的同时招募和失活。
The positive transcription elongation factor ( P-TEFb) comprises a kinase, CDK9, and a Cyclin T1 or T2. Its activity is inhibited by association with the HEXIM1 or HEXIM2 protein bound to 7SK small nuclear RNA. HEXIM1 and HEXIM2 were found to form stable homo- and hetero-oligomers. Using yeast two-hybrid and transfection assays, we have now shown that the C-terminal domains of HEXIM proteins directly interact with each other. Hydrodynamic parameters measured by glycerol gradient ultracentrifugation and gel-permeation chromatography demonstrate that both purified recombinant and cellular HEXIM1 proteins form highly anisotropic particles. Chemical cross-links suggest that HEXIM1 proteins form dimers. The multimeric nature of HEXIM1 is maintained in P-TEFb(.)HEXIM1(.)7SK RNA complexes. Multiple P-TEFb modules are found in the inactive P-TEFb(.)HEXIM1(.)7SK complexes. It is proposed that 7SK RNA binding to a HEXIM1 multimer promotes the simultaneous recruitment and hence inactivation of multiple P-TEFb units.