Deciphering the Roles of the Histone H2B N-Terminal Domain in Genome-Wide Transcription

Abstract

Histone N-terminal domains are frequent targets of posttranslational modifications. Multiple acetylated lysine residues have been identified in the N-terminal domain of H2B (K6, K11, K16, K17, K21, and K22), but little is known about how these modifications regulate transcription. We systematically mutated the N-terminal domain of histone H2B, both at known sites of lysine acetylation and elsewhere, and characterized the resulting changes in genome-wide expression in each mutant strain. Our results indicate that known sites of lysine acetylation in this domain are required for gene-specific transcriptional activation. However, the entire H2B N-terminal domain is principally required for the transcriptional repression of a large subset of the yeast genome. We find that the histone H2B repression (HBR) domain, comprised of residues 30 to 37, is necessary and sufficient for this repression. Many of the genes repressed by the HBR domain are located adjacent to telomeres or function in vitamin and carbohydrate metabolism. Deletion of the HBR domain also confers an increased sensitivity to DNA damage by UV irradiation. We mapped the critical residues in the HBR domain required for its repression function. Finally, comparisons of these data with previous studies reveal that a surprising number of genes are coregulated by the N-terminal domains of histone H2B, H3, and H4.

Supplemental material for this article may be found at http://mcb.asm.org/.

We are grateful to Bill Davis, Lisa Gloss, Ray Reeves, Amy Rodriguez, and Michael Smerdon for helpful discussions and comments on the manuscript. We thank Richard Young for the generous gift of the yeast strain Z1256. We thank Jason Sikes for software and web support. We thank Julie Stanton and Yi Jin for performing the histone H2B Western blots.

This work was supported by American Cancer Society grant RSG-03-181-01-GMC. D.F. was supported by NIH grant ES04106 from the National Institute of Environmental Health Sciences (NIEHS) to Michael J. Smerdon.