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Genes Dev. 2005 Mar 15;19(6):677-82.

Replication-independent core histone dynamics at transcriptionally active loci in vivo.

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  • 1Department of Biochemistry and Biophysics, University of Rochester Medical Center, Rochester, New York 14642, USA.

Abstract

We used a novel labeling technique in the naturally synchronous organism Physarum polycephalum to examine the fate of core histones in G2 phase. We find rapid exchange of H2A/H2B dimers with free pools that is greatly diminished by treatment of the cells with alpha-amanitin. This exchange is enhanced in pol II-coding sequences compared with extragenic regions or inactive loci. In contrast, H3/H4 tetramers exhibit far lower levels of exchange in the pol II-transcribed genes tested, suggesting that tetramer exchange occurs via a distinct mechanism. However, we find that transcribed regions of the ribosomal RNA gene loci exhibit rapid exchange of H3/H4 tetramers. Thus, our data show that the majority of the pol II transcription-dependent histone exchange is due to elongation in vivo rather than promoter remodeling or other pol II-dependent alterations in promoter structure and, in contrast to pol I, pol II transcription through nucleosomes in vivo causes facile exchange of both H2A/H2B dimers while allowing conservation of epigenetic "marks" and other post-translational modifications on H3 and H4.

PMID:
15769942
[PubMed - indexed for MEDLINE]
PMCID:
PMC1065721
Free PMC Article

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