In order to maintain a specific chroma-tin state, modified histones must remain attached to template DNA during transcription. In fact, RNA polymerase II can transcribe the nucleosome template without changing nucleosome positioning. Recently, Spt6, a highly conserved polymerase-associated histone chaperone, was shown to prevent transcription-coupled loss of posttranslationally modified histone H3. Now, Kato et al. propose here that Spt6 has two fundamentally distinct functions in the regulation of histone modification: one is to act as a platform for histone modifiers and the other is as a molecular liaison between histone molecules and template DNA, preventing cotranscriptional dissociation of preexisting histones so that locus-specific modifications are maintained.
展开▼
