Fig. 4
From: Functions of HP1 proteins in transcriptional regulation
Self-propagation of heterochromatin by the interaction of HP1a and Su(var)3-9. A The Drosophila HP1 ortholog HP1a recognizes and binds H3K9me2/3 (light green) through its CD (green oval). It subsequently recruits the H3K9 methyltransferase Su(var)3-9 (orange oval) to these loci through its CSD (teal oval). B Once recruited by HP1a, Su(var)3-9 deposits H3K9me2/3 modifications on nearby nucleosomes (blue). C The newly deposited H3K9me2 modifications serve as novel binding sites for additional HP1a proteins. Binding of HP1a at these tails subsequently results in further recruitment of Su(var)3-9, and the process continues. Propagation of HP1a results in formation of heterochromatin and compaction of chromatin structure