Methylation-independent binding to histone H3 and cell cycle-dependent incorporation of HP1beta into heterochromatin
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Dialynas, G. K.
Makatsori, D.
Kourmouli, N.
Theodoropoulos, P. A.
McLean, K.
Terjung, S.
Singh, P. B.
Georgatos, S. D.
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peer-reviewed
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J Biol Chem
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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.
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Amino Acid Sequence, Animals, Cell Cycle, Cell Nucleus/metabolism, Chromosomal Proteins, Non-Histone/*chemistry, Dogs, HeLa Cells, Heterochromatin/*chemistry, Histones/*chemistry, Humans, Methylation, Molecular Sequence Data, Protein Binding, Rats
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http://www.ncbi.nlm.nih.gov/pubmed/16547356
http://www.jbc.org/content/281/20/14350.full.pdf
http://www.jbc.org/content/281/20/14350.full.pdf
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en
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Πανεπιστήμιο Ιωαννίνων. Σχολή Επιστημών Υγείας. Τμήμα Ιατρικής