TAF1 Histone Acetyltransferase Activity in Sp1 Activation of the Cyclin D1 Promoter

Abstract

A missense mutation within the histone acetyltransferase (HAT) domain of the TATA binding protein-associated factor TAF1 induces ts13 cells to undergo a late G₁ arrest and decreases cyclin D1 transcription. We have found that TAF1 mutants (Δ844-850 and Δ848-850, from which amino acids 844 through 850 and 848 through 850 have been deleted, respectively) deficient in HAT activity are unable to complement the ts13 defect in cell proliferation and cyclin D1 transcription. Chromatin immunoprecipitation assays revealed that histone H3 acetylation was reduced at the cyclin D1 promoter but not the c-fos promoter upon inactivation of TAF1 in ts13 cells. The hypoacetylation of H3 at the cyclin D1 promoter was reversed by treatment with trichostatin A (TSA), a histone deacetylase inhibitor, or by expression of TAF1 proteins that retain HAT activity. Transcription of a chimeric promoter containing the Sp1 sites of cyclin D1 and c-fos core remained TAF1 dependent in ts13 cells. Treatment with TSA restored full activity to the cyclin D1-c-fos chimera at 39.5°C. In vivo genomic footprinting experiments indicate that protein-DNA interactions at the Sp1 sites of the cyclin D1 promoter were compromised at 39.5°C in ts13 cells. These data have led us to hypothesize that TAF1-dependent histone acetylation facilitates transcription factor binding to the Sp1 sites, thereby activating cyclin D1 transcription and ultimately G₁-to-S-phase progression.

ACKNOWLEDGMENTS

We are indebted to K. Lewis for excellent technical support with tissue culture and molecular biology and Y. Kawata and K. Bomsztyk for assistance with the chromatin immunoprecipitation protocol. We thank R. Tjian for kindly providing the anti-HA ascites fluid, X. F. Wang for the Gal4 and Gal4-Sp1 fusion expression constructs, I. Davidson for the mouse TAF4 antibody, and S. Bajjalieh and K. Bomsztyk for critical reading of the manuscript. We especially thank past and present members of the Wang lab, including K. Lewis, R. Squillace, and K. White, for valuable discussions and support of this research.

T.L.H. was supported in part by National Research Service Award GM7750 from the National Institute of General Medical Sciences. E.L.D. was supported in part by National Research Service Award T32 GM07270 from the National Institute of General Medical Sciences. This work was supported by research project grants RPG-98-201-CCG and RSG-04-234-01-GMC from the American Cancer Society.