Rad6-dependent ubiquitination of histone H2B in yeast.

Although ubiquitinated histones are present in substantial levels in vertebrate cells, the roles they play in specific biological processes and the cellular factors that regulate this modification are not well characterized. Ubiquitinated H2B (uH2B) has been identified in the yeast Saccharomyces cerevisiae, and mutation of the conserved ubiquitination site is shown to confer defects in mitotic cell growth and meiosis. uH2B was not detected in rad6 mutants, which are defective for the ubiquitin-conjugating enzyme Ubc2, thus identifying Rad6 as the major cellular activity that ubiquitinates H2B in yeast.