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Histone codes

The histone code hypothesis posits that distinct combinations of histone modifications can recruit chromatin-modifying enzymes and exert epigenetic control over heterochromatin assembly. In the March 15 ScienceXpress, Nakayama et al. describe a role for histone methylation in heterochromatin assembly in the fission yeast Schizosaccharomyces pombe. The Clr4 protein methylated lysine 9 of histone H3 (H3Lys9) preferentially within heterochromatin-associated regions. H3Lys9 methylation led to the recruitment of the chromodomain protein Swi6, a homolog of Drosophila HP1. Both methylation and recruitment were dependent on activity of the histone deacetylase Clr3. Chromatin assembly by Swi6/Clr4 at the mating-type locus results in silencing. Hence, sequential deacetylation and methylation of histone tails leads ultimately to epigenetic inheritance patterns.


  1. The language of covalent histone modifications.

  2. ScienceXpress, []

  3. Role of Histone H3 Lysine 9 Methylation in Epigenetic Control of Heterochromatin Assembly, []

  4. The chromo and SET domains of the Clr4 protein are essential for silencing in fission yeast.

  5. The chromodomain protein Swi6: a key component at fission yeast centromeres.

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Weitzman, J.B. Histone codes. Genome Biol 2, spotlight-20010319-01 (2001).

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