Figure 5.
Self-perpetuating model for heterochromatin expansion. Repetitive elements such as retrotransposons produce dsRNAs that trigger the RNAi pathway. This results in the targeting of DNA and histone methyltransferases to retrotransposons resident on host chromosomes. Histone modification (e.g., H3 methyl-K9) establishes heterochromatin and, in turn, creates recognition sites for retrotransposon integrases. The targeting of retrotransposons to the domain of heterochromatin serves to reinforce the epigenetic mark.
