H2A.Z Is Required for Global Chromatin Integrity and for Recruitment of RNA Polymerase II under Specific Conditions

Abstract

Evolutionarily conserved variant histone H2A.Z has been recently shown to regulate gene transcription in Saccharomyces cerevisiae. Here we show that loss of H2A.Z in this organism negatively affects the induction of GAL genes. Importantly, fusion of the H2A.Z C-terminal region to S phase H2A without its corresponding C-terminal region can mediate the variant histone's specialized function in GAL1-10 gene induction, and it restores the slow-growth phenotype of cells with a deletion of HTZ1. Furthermore, we show that the C-terminal region of H2A.Z can interact with some components of the transcriptional apparatus. In cells lacking H2A.Z, recruitment of RNA polymerase II and TATA-binding protein to the GAL1-10promoters is significantly diminished under inducing conditions. Unexpectedly, we also find that H2A.Z is required to globally maintain chromatin integrity under GAL gene-inducing conditions. We hypothesize that H2A.Z can positively regulate gene transcription, at least in part, by modulating interactions with RNA polymerase II-associated factors at certain genes under specific cell growth conditions.

ACKNOWLEDGMENTS

This work was supported by grants from the CIHR and NSERC of Canada and the FCAR of Québec to L.G. F.R. holds a fellowship from the NCI of Canada; L.G. is a research scholar of the CIHR/CRS Inc. of Canada.

We are grateful to Mary Ann Osley for gifts of yeast strains and Gerard Evan for the 9E11 hybridoma cell line. We thank Martin Gorovsky, Jocelyn Beaucher, and Karine Lemieux for discussions and comments on the manuscript. We also thank Nancy Hannett for the Myc tagging of H2A and H2A.Z and Daniel Paradis for technical help. We are especially thankful to Richard Young for all of his support during the course of this study.

M.A., F.R., and M.L. contributed equally to this work.