Writing and reading H2B monoubiquitylation.

Monoubiquitylation of histone H2B (H2Bub1), catalyzed by the heterodimeric ubiquitin ligase complex RNF20/40, regulates multiple molecular and biological processes. The addition of a large ubiquitin moiety to the small H2B is believed to change the biochemical features of the chromatin. H2B monoubiquitylation alters nucleosome stability, nucleosome reassembly and higher order compaction of the chromatin. While these effects explain some of the direct roles of H2Bub1, there is growing evidence that H2Bub1 can also regulate multiple DNA-templated processes indirectly, by recruitment of specific factors ("readers") to the chromatin. H2Bub1 readers mediate much of the effect of H2Bub1 on histone crosstalk, transcriptional outcome and probably other chromatin-related activities. Here we summarize the current knowledge about H2Bub1-specific readers and their role in various biological processes. This article is part of a Special Issue entitled: Molecular mechanisms of histone modification function.