Methylation-independent binding to histone H3 and cell cycle-dependent incorporation of HP1beta into heterochromatin

George K Dialynas, Dimitra Makatsori, Niki Kourmouli, Panayiotis A Theodoropoulos, Kevin McLean, Stefan Terjung, Prim B Singh, Spyros D Georgatos

Research output: Contribution to journalArticlepeer-review

28 Citations (Scopus)

Abstract

We have examined HP1beta-chromatin interactions in different molecular contexts in vitro and in vivo. Employing purified components we show that HP1beta exhibits selective, stoichiometric, and salt-resistant binding to recombinant histone H3, associating primarily with the helical "histone fold" domain. Furthermore, using "bulk" nucleosomes released by MNase digestion, S-phase extracts, and fragments of peripheral heterochromatin, we demonstrate that HP1beta associates more tightly with destabilized or disrupted nucleosomes (H3/H4 subcomplexes) than with intact particles. Western blotting and mass spectrometry data indicate that HP1beta-selected H3/H4 particles and subparticles possess a complex pattern of posttranslational modifications but are not particularly enriched in me3K9-H3. Consistent with these results, mapping of HP1beta and me3K9-H3 sites in vivo reveals overlapping, yet spatially distinct patterns, while transient transfection assays with synchronized cells show that stable incorporation of HP1beta-gfp into heterochromatin requires passage through the S-phase. The data amassed challenge the dogma that me3K9H3 is necessary and sufficient for HP1 binding and unveil a new mode of HP1-chromatin interactions.

Original languageEnglish
Pages (from-to)14350-60
Number of pages11
JournalJournal of Biological Chemistry
Volume281
Issue number20
DOIs
Publication statusPublished - May 19 2006

Keywords

  • Amino Acid Sequence
  • Animals
  • Cell Cycle
  • Cell Nucleus
  • Chromosomal Proteins, Non-Histone
  • Dogs
  • HeLa Cells
  • Heterochromatin
  • Histones
  • Humans
  • Methylation
  • Molecular Sequence Data
  • Protein Binding
  • Rats
  • Journal Article
  • Research Support, Non-U.S. Gov't

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