Jacob, Y., Bergamin, E., Donoghue, M. T., Mongeon, V., LeBlanc, C., Voigt, P., Underwood, C. J., Brunzelle, J. S., Michaels, S. D., Reinberg, D., Couture, J. F., Martienssen, R. A. (March 2014) Selective methylation of histone H3 variant H3.1 regulates heterochromatin replication. Science, 343 (6176). pp. 1249-53. ISSN 0036-8075
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Abstract
Histone variants have been proposed to act as determinants for posttranslational modifications with widespread regulatory functions. We identify a histone-modifying enzyme that selectively methylates the replication-dependent histone H3 variant H3.1. The crystal structure of the SET domain of the histone H3 lysine-27 (H3K27) methyltransferase ARABIDOPSIS TRITHORAX-RELATED PROTEIN 5 (ATXR5) in complex with a H3.1 peptide shows that ATXR5 contains a bipartite catalytic domain that specifically "reads" alanine-31 of H3.1. Variation at position 31 between H3.1 and replication-independent H3.3 is conserved in plants and animals, and threonine-31 in H3.3 is responsible for inhibiting the activity of ATXR5 and its paralog, ATXR6. Our results suggest a simple model for the mitotic inheritance of the heterochromatic mark H3K27me1 and the protection of H3.3-enriched genes against heterochromatization during DNA replication.
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