Figure 2.

Schematic model for the functional role of H4K20me1 in centrochromatin. The CENP-A-H4 complex is associated with the CENP-A chaperone HJURP, and has been shown to be incorporated into centromeres during early G1 phase of the cell cycle. Given that H4 subunits in CENP-A nucleosomes have been found to be consistently methylated at K20, it is likely that this modification occurs just after CENP-A incorporation by PR-Set7. This would allow various Constitutive-Centromere-Associated-Network (CCAN) proteins to recognize H4K20me1 in centrochromatin, and thereby assemble kinetochores. It is vital that future research elucidates the timing and mechanisms by which CCAN proteins mediate kinetochore assembly.