Selective requirements for histone H3 and H4 N termini in p300-dependent transcriptional activation from chromatin.

The N-terminal tails of the core histones play important roles in transcriptional regulation, but their mechanism(s) of action are poorly understood. Here, pure chromatin templates assembled with varied combinations of recombinant wild-type and mutant core histones have been employed to ascertain the role of individual histone tails, both in overall acetylation patterns and in transcription. In vitro assays show an indispensable role for H3 and H4 tails, especially major lysine substrates, in p300-dependent transcriptional activation, as well as activator-targeted acetylation of promoter-proximal histone tails by p300. These results indicate, first, that constraints to transcription are imposed by nucleosomal histone components other than histone N-terminal tails and, second, that the histone N-terminal tails have selective roles, which can be modulated by targeted acetylation, in transcriptional activation by p300.