Hofmann Wilma A, Stojiljkovic Ljuba, Fuchsova Beata, Vargas Gabriela M, Mavrommatis Evangelos, Philimonenko Vlada, Kysela Katarina, Goodrich James A, Lessard James L, Hope Thomas J, Hozak Pavel, de Lanerolle Primal
Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA.
Nat Cell Biol. 2004 Nov;6(11):1094-101. doi: 10.1038/ncb1182. Epub 2004 Oct 24.
Actin is abundant in the nucleus and has been implicated in transcription; however, the nature of this involvement has not been established. Here we demonstrate that beta-actin is critically involved in transcription because antibodies directed against beta-actin, but not muscle actin, inhibited transcription in vivo and in vitro. Chromatin immunoprecipitation assays demonstrated the recruitment of actin to the promoter region of the interferon-gamma-inducible MHC2TA gene as well as the interferon-alpha-inducible G1P3 gene. Further investigation revealed that actin and RNA polymerase II co-localize in vivo and also co-purify. We employed an in vitro system with purified nuclear components to demonstrate that antibodies to beta-actin block the initiation of transcription. This assay also demonstrates that beta-actin stimulates transcription by RNA polymerase II. Finally, DNA-binding experiments established the presence of beta-actin in pre-initiation complexes and also showed that the depletion of actin prevented the formation of pre-initiation complexes. Together, these data suggest a fundamental role for actin in the initiation of transcription by RNA polymerase II.
肌动蛋白在细胞核中含量丰富，并与转录有关；然而，这种关联的本质尚未明确。在此我们证明，β - 肌动蛋白在转录过程中起关键作用，因为针对β - 肌动蛋白而非肌肉肌动蛋白的抗体在体内和体外均能抑制转录。染色质免疫沉淀分析表明，肌动蛋白被募集到干扰素 - γ 诱导的MHC2TA基因以及干扰素 - α 诱导的G1P3基因的启动子区域。进一步研究发现，肌动蛋白与RNA聚合酶II在体内共定位且能共同纯化。我们利用一个含有纯化核成分的体外系统证明，针对β - 肌动蛋白的抗体可阻断转录起始。该实验还表明，β - 肌动蛋白可刺激RNA聚合酶II进行转录。最后，DNA结合实验证实了预起始复合物中存在β - 肌动蛋白，并且还表明肌动蛋白的缺失会阻止预起始复合物的形成。这些数据共同表明，肌动蛋白在RNA聚合酶II介导的转录起始过程中发挥着重要作用。
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