Fig. 3.

Epigenetic regulations of retrotransposons by DNA methylation and H3K9me3 modification. a Schematic diagram of different forms in retrotransposon repression. a piRNA-pathway is the most common mechanism to regulate retrotransposons in germ cells; piRNA guides PIWI protein to bind transposon transcripts, which have a matching sequence, and cleave target RNA. In addition, piRNAs work not only at the post-transcriptional level, but also regulate DNA methylation and histone modification. b KAP1/Trim28 complex is important in retrotransposons repression in early embryogenesis and ESCs. In this mechanism, KRAB-ZFPs recruit KAP1 to repress transcription of targeted retrotransposon, and KAP1 represses genes by recruiting histone methyltransferases SETDB1, HP1, and NuRD histone deacetylase complex