Interaction between RNA, histone modification, and DNA methylation in heritable silencing.

Histone deacetylation and other modifications, particularly the methylation of lysine 9 within histone H3 (H3-K9) residues located in the histone tails, cause chromatin condensation and block transcriptional initiation. Histone modification can also attract DNA methyltransferases to initiate cytosine methylation, which in turn can reinforce histone modification patterns conducive to silencing. Experiments in yeast and plants have clearly shown the involvement of RNA interference in the establishment of heterochromatic states and silencing. RNA triggering of heritable quiescence might therefore also be involved in higher organisms.