Epigenetic gene silencing by heterochromatin primes fungal resistance.

Heterochromatin that depends on histone H3 lysine 9 methylation (H3K9me) renders embedded genes transcriptionally silent. In the fission yeast Schizosaccharomyces pombe, H3K9me heterochromatin can be transmitted through cell division provided the counteracting demethylase Epe1 is absent. Heterochromatin heritability might allow wild-type cells under certain conditions to acquire epimutations, which could influence phenotype through unstable gene silencing rather than DNA change.

Epigenetics. Restricted epigenetic inheritance of H3K9 methylation.

Posttranslational histone modifications are believed to allow the epigenetic transmission of distinct chromatin states, independently of associated DNA sequences. Histone H3 lysine 9 (H3K9) methylation is essential for heterochromatin formation; however, a demonstration of its epigenetic heritability is lacking. Fission yeast has a single H3K9 methyltransferase, Clr4, that directs all H3K9 methylation and heterochromatin.