Methylation of Histone H3 by COMPASS Requires Ubiquitination of Histone H2B by Rad6

摘要

Post-translational modifications of the histone protein amino-termini, or "tails," play an important role in the epigenetic regulation of gene expression in eukaryotes. The various types of these modifications include acetylation, phosphorylation, methylation, ubiquitination, and ADP-ribosylation. Acetylation is the best characterized of these modifications and elucidation of a functional model of acetylation has led to the development of the "histone code" hypothesis. This "histone code" predicts that clusters of site-specific histone-tail modifications provide recognition "codes" for the binding or activity of ancillary proteins that evoke specific changes in chromatin structure that contributes to gene regulation. These modifications may also be interdependent, occurring exclusively or in a mutual fashion. Characterization of other modifications, such as histone H3 phosphorylation and methylation, has supported the predictions made by the histone code ypothesis, and has defined a role for these modifications in gene regulation. Thus, the discovery of multiple histone methyltransferases (HMTs) in different organisms has led to increased interest in elucidating the mechanism by which this type of modification is brought about.