Phosphorylation-Dependent Regulation of Cyclin D1 and Cyclin A Gene Transcription by TFIID Subunits TAF1 and TAF7

Abstract

The largest transcription factor IID (TFIID) subunit, TBP-associated factor 1 (TAF1), possesses protein kinase and histone acetyltransferase (HAT) activities. Both enzymatic activities are essential for transcription from a subset of genes and G₁ progression in mammalian cells. TAF7, another TFIID subunit, binds TAF1 and inhibits TAF1 HAT activity. Here we present data demonstrating that disruption of the TAF1/TAF7 interaction within TFIID by protein phosphorylation leads to activation of TAF1 HAT activity and stimulation of cyclin D1 and cyclin A gene transcription. Overexpression and small interfering RNA knockdown experiments confirmed that TAF7 functions as a transcriptional repressor at these promoters. Release of TAF7 from TFIID by TAF1 phosphorylation of TAF7 increased TAF1 HAT activity and elevated histone H3 acetylation levels at the cyclin D1 and cyclin A promoters. Serine-264 of TAF7 was identified as a substrate for TAF1 kinase activity. Using TAF7 S264A and S264D phosphomutants, we determined that the phosphorylation state of TAF7 at S264 influences the levels of cyclin D1 and cyclin A gene transcription and promoter histone H3 acetylation. Our studies have uncovered a novel function for the TFIID subunit TAF7 as a phosphorylation-dependent regulator of TAF1-catalyzed histone H3 acetylation at the cyclin D1 and cyclin A promoters.

ACKNOWLEDGMENTS

Many thanks are given to A. Weinmann and K. Bomsztyk for critical reading of the manuscript and providing insightful comments. We are indebted to R. Moon for the TAP-tagged expression plasmid, C. Hague for the YFP expression plasmid, and D. Singer for the FLAG-TAF7 expression construct. We also thank R. Tjian, X. Liu, and I. Davidson for generously providing antibodies for TBP, TAF1, and TAF7, respectively. We especially thank members of the Wang lab for invaluable technical support and discussions.

S.L.K was supported in part by Public Health Service, National Research Service Award, training grant 2T32 GM007270, from the National Institute of General Medical Sciences. This work was supported by research grant RSG-04-234-01-GMC from the American Cancer Society and by bridge funding from the University of Washington.