Nature Cell Biology6, 1094 - 1101 (2004)
Published online: 24 October 2004; | doi:10.1038/ncb1182
Actin is part of pre-initiation complexes and is necessary for transcription by RNA polymerase II
Wilma A. Hofmann1, Ljuba Stojiljkovic1, Beata Fuchsova1, Gabriela M. Vargas1, Evangelos Mavrommatis1, Vlada Philimonenko2, Katarina Kysela2, James A. Goodrich3, James L. Lessard4, Thomas J. Hope5, Pavel Hozak2
& Primal de Lanerolle1
1
Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA.
2
Department of Cell Ultrastructure and Molecular Biology, Institute of Experimental Medicine, Academy of Sciences of the Czech Republic, Prague 142 20, Czech Republic.
3
Department of Chemistry and Biochemistry, University of Colorado, Boulder, CO 80309, USA.
4
Division of Developmental Biology, Children's Hospital Research Foundation, Cincinnati, OH 45229, USA.
5
Department of Microbiology and Immunology, University of Illinois at Chicago, Chicago, IL 60612, USA.
Correspondence should be addressed to Primal de Lanerolle primal@uic.edu
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 -actin is critically involved in transcription because antibodies directed against -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--inducible MHC2TA gene as well as the interferon--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 -actin block the initiation of transcription. This assay also demonstrates that -actin stimulates transcription by RNA polymerase II. Finally, DNA-binding experiments established the presence of -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.
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-actin is critically involved in transcription because antibodies directed against 
-inducible MHC2TA gene as well as the interferon-
-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 
