Actin is part of pre-initiation complexes and is necessary for transcription by RNA polymerase II.
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.
Hofmann
Wilma A
WA
Department of Physiology and Biophysics, University of Illinois at Chicago, Chicago, IL 60612, USA.
Stojiljkovic
Ljuba
L
Fuchsova
Beata
B
Vargas
Gabriela M
GM
Mavrommatis
Evangelos
E
Philimonenko
Vlada
V
Kysela
Katarina
K
Goodrich
James A
JA
Lessard
James L
JL
Hope
Thomas J
TJ
Hozak
Pavel
P
de Lanerolle
Primal
P
D000199:Actins / Q000502:physiology*; D001483:Base Sequence; D017931:DNA Primers; D006367:HeLa Cells; D006801:Humans; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins / Q000235:genetics; D011401:Promoter Regions, Genetic; D011506:Proteins / Q000235:genetics; D012319:RNA Polymerase II / Q000502:physiology*; D015534:Trans-Activators / Q000235:genetics; D014158:Transcription, Genetic / Q000502:physiology*
D000199:Actins; D017931:DNA Primers; C468762:IFI6 protein, human; C083728:MHC class II transactivator protein; D024101:Mitochondrial Proteins; D009687:Nuclear Proteins; D011506:Proteins; D015534:Trans-Activators; D012319:RNA Polymerase II