Figure 6.

A model illustrating possible roles for HP1a and Piwi in PHeMAAH. In this model, nucleosomes (gray) from two homologs are physically connected by dimers of HP1a. HP1a chromodomains (green) bind to the chromatin at the H3K9 methyl mark (yellow star) and dimerize via interactions at their CSDs (dark blue). Piwi (light blue), along with an associated RNA (red), binds to the HP1a dimer at the CSD-CSD surface. The Piwi-associated RNA provides sequence specificity by interacting with the DNA sequence via (A) RNA-DNA hybridzation or (B) hybridization to a second RNA (orange), such as a nascent transcript, emerging from the DNA (black).