Stimulation of CREB Binding Protein Nucleosomal Histone Acetyltransferase Activity by a Class of Transcriptional Activators

Abstract

The transcriptional coactivator CREB binding protein (CBP) possesses intrinsic histone acetyltransferase (HAT) activity that is important for gene regulation. CBP binds to and cooperates with numerous nuclear factors to stimulate transcription, but it is unclear if these factors modulate CBP HAT activity. Our previous work showed that CBP interacts with the Epstein-Barr virus-encoded basic region zipper (b-zip) protein, Zta, and augments its transcriptional activity. Here we report that Zta strongly enhances CBP-mediated acetylation of nucleosomal histones. Zta stimulated the HAT activity of CBP that had been partially purified or immunoprecipitated from mammalian cells as well as from affinity-purified, baculovirus expressed CBP. Stimulation of nucleosome acetylation required the CBP HAT domain, the Zta DNA binding and transcription activation domain, and nucleosomal DNA. In addition to Zta, we found that two other b-zip proteins, NF-E2 and C/EBPα, strongly stimulated nucleosomal HAT activity. In contrast, several CBP-binding proteins, including phospho-CREB, JUN/FOS, GATA-1, Pit-1, and EKLF, failed to stimulate HAT activity. These results demonstrate that a subset of transcriptional activators enhance the nucleosome-directed HAT activity of CBP and suggest that nuclear factors may regulate transcription by altering substrate recognition and/or the enzymatic activity of chromatin modifying coactivators.

ACKNOWLEDGMENTS

We thank Dimitrios Thanos for generously providing baculovirus H6-CBP and Shelley Berger and members of her laboratory for instruction in acetylation assays. We are grateful to Volker Blank for providing the tethered NF-E2 construct, Ramin Shiekhattar for CREB protein, Xiangyuan Wang for purification of core histones, T. Kerppola for Jun and Fos proteins, and Hsiao-Ling Hung for GST fusion proteins.

This work was supported by grants from NIH (GM 54687), the Edward Mallinckrodt, Jr. Foundation, and the Leukemia & Lymphoma Society (to P.M.L.) and an NCI Core Grant to the Wistar Institute. G.A.B. was supported by a grant from NIH (RO1 DK54937-01) and by the American Society of Hematology Scholar Award.