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Nat Genet. 2004 May;36(5):502-6. Epub 2004 Apr 18.

Dynamic assembly of silent chromatin during thymocyte maturation.

Author information

1
Howard Hughes Medical Institute and Department of Microbiology, Immunology, and Molecular Genetics, University of California, Los Angeles, California 90095-1662, USA.

Abstract

Considerable knowledge has been gained from temporal analyses of molecular events culminating in gene activation, but technical hurdles have hindered comparable studies of gene silencing. Here we describe the temporal assembly of silent chromatin at the mouse terminal transferase gene (Dntt), which is silenced and repositioned to pericentromeric heterochromatin during thymocyte maturation. Silencing was nucleated at the Dntt promoter by the ordered deacetylation of histone H3 at Lys9 (H3-Lys9), loss of methylation at H3-Lys4 and acquisition of methylation at H3-Lys9, followed by bidirectional spreading of each event. Deacetylation at H3-Lys9 coincided with pericentromeric repositioning, and neither of these early events required de novo protein synthesis. CpG methylation increased primarily in mature T cells that had left the thymus. A transformed thymocyte line supported reversible inactivation of Dntt without repositioning. In these cells, histone modification changes were nucleated at the promoter but did not spread. These results provide a foundation for elucidating the mechanisms of silent chromatin assembly during development.

PMID:
15098035
DOI:
10.1038/ng1351
[Indexed for MEDLINE]

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