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© The Rockefeller University Press,
0021-9525/1999//1153 $5.00
The Journal of Cell Biology, Volume 147, Number 6,
, 1999 1153-1166
Original Article |
Duplication and Maintenance of Heterochromatin Domains
almouzni{at}curie.fr
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 (Hp1
and -β), and chromatin assembly factor 1 (CAF-1). During replication, Hp1
and -β 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 Hp1
and -β, and that a degree of plasticity is provided by the cycle of H4 acetylation/deacetylation assisted by CAF-1.
Key Words: heterochromatin nuclear organization histone H4 acetylation chromatin assembly factor 1 heterochromatin protein 1
© 1999 The Rockefeller University Press
. Abbreviations used in this paper: BiodU, Biotin-16-deoxyuridine; BrdU, 5-bromo-2'-deoxyuridine; CAF-1, chromatin assembly factor 1; H4Ac n, histone H4 acetylated at lysine n; HAT, histone acetyl transferase; HDAC, histone deacetylase; HP1, heterochromatin protein 1; pAb, polyclonal antibody; TSA, Trichostatin A.
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