Figure 1.

Pathway for heterochromatin establishment. Major satellite repeats can be recognized by 2 transcription factors (Pax3 and Pax9). Binding of these factors is crucial to mediate recruitment of Suv39h enzymes that establish H3K9me3 at pericentric heterochromatin. For full activity Suv39h enzymes require H3K9me1 as substrate, which is deposited at heterochromatin from a cytoplasmic pool generated by Prdm3 and Prdm16. Once H3K9me3 is established at heterochromatin, HP1 proteins can bind to this modification. Suv4-20h2 can then stably associate with regions of high HP1 occupancy and mediate H4K20me3. Suv4-20h2 has additional roles in mediating chromatin compaction and recruitment of cohesin.