Putting the Pieces Together: Histone H2B Ubiquitylation Directly Stimulates Histone H3K79 Methylation

Employing an in vitro reconstruction approach, McGinty et al. studied the mechanism of stimulation of the Dot1-catalysed histone H3 methylation at Lys79 by histone H2B ubiquitylation at Lys120. To generate nucleosome particles that carry the uniquitylation at Lys120, they chemically connected three polypeptides the main parts of histone He and ubiquitin expressed in bacteria and a branched synthetic peptide. Using the semisynthetically produced nucleosome substrates and purified Dot1 enzyme, they showed that Dot1 is directly stimulated by the ubiquitylation, thus ruling out the need for further protein factorss to mediate the effect.