Duplication and maintenance of heterochromatin domains.
To investigate the mechanisms that assure the maintenance of heterochromatin regions, we took advantage of the fact that clusters of heterochromatin DNA replicate late in S phase and are processed in discrete foci with a characteristic nuclear distribution. At the light microscopy level, within these entities, we followed DNA synthesis, histone H4 acetylation, heterochromatin protein 1 (Hp1alpha and -beta), and chromatin assembly factor 1 (CAF-1). During replication, Hp1alpha and -beta domains of concentration are stably maintained, whereas heterochromatin regions are enriched in both CAF-1 and replication-specific acetylated isoforms of histone H4 (H4Ac 5 and 12). We defined a time window of 20 min for the maintenance of this state. Furthermore, treatment with Trichostatin A (TSA), during and after replication, sustains the H4Ac 5 and 12 state in heterochromatin excluding H4Ac 8 and 16. In comparison, early replication foci, at the same level, did not display any specific enrichment in H4Ac 5 and 12. These data emphasize the specific importance for heterochromatin of the replication-associated H4 isoforms. We propose that perpetuation of heterochromatin involves self-maintenance factors, including local concentration of Hp1alpha and -beta, and that a degree of plasticity is provided by the cycle of H4 acetylation/deacetylation assisted by CAF-1.
Taddei
A
A
Institut Curie, Research section, UMR 144 et 218 du Centre National de la Recherche Scientifique (CNRS), 75248 Paris cedex 05, France.
Roche
D
D
Sibarita
J B
JB
Turner
B M
BM
Almouzni
G
G
D000107:Acetylation / Q000187:drug effects; D000818:Animals; D002460:Cell Line; D056504:Chromatin Assembly Factor-1; D000090266:Chromobox Protein Homolog 5; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D004247:DNA / Q000096:biosynthesis / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D004268:DNA-Binding Proteins / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D006367:HeLa Cells; D006570:Heterochromatin / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D056572:Histone Deacetylase Inhibitors; D006655:Histone Deacetylases / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D006801:Humans; D006877:Hydroxamic Acids / Q000494:pharmacology; D051379:Mice; D020033:Protein Isoforms / Q000378:metabolism; D016196:S Phase / Q000235:genetics; D013997:Time Factors
C000715594:CBX5 protein, human; C533593:CHAF1B protein, human; D056504:Chromatin Assembly Factor-1; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D006570:Heterochromatin; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D020033:Protein Isoforms; D000090266:Chromobox Protein Homolog 5; C012589:trichostatin A; D004247:DNA; D006655:Histone Deacetylases