Sir2 deacetylates histone H3 lysine 56 to regulate telomeric heterochromatin structure in yeast.

摘要: Summary At telomeric heterochromatin in yeast, the Sir protein complex spreads from Rap1 sites to silence adjacent genes. This cascade is believed occur when Sir2, an NAD + -dependent enzyme, deacetylates histone H3 and H4 N termini, particular K16, enabling more binding. Lysine 56 of located at entry-exit points DNA superhelix surrounding nucleosome, where it may control compaction. We have found that K56 substitutions disrupt silencing severely without decreasing binding at telomere. Our vitro vivo data indicate Sir2 directly compact chromatin prevent access RNA polymerase ectopic bacterial dam methylase. Since spread proteins necessary but not sufficient for silencing, we propose occurs close nucleosomal gates, enabling compaction heterochromatin.