H2A.Z Facilitates Licensing and Activation of Early Replication Origins

DNA replication is a tightly regulated process that ensures the precise duplication of the genome during cell cycle. Licensing and activation of eukaryotic replication origins are controlled primarily by chromatin. However, the chromatin features involved and the regulatory mechanism remain largely unknown. In this study, we found that H2A.Z binds Suv420H1 directly to promote H4K20me2 deposition on nucleosome both in vitro and in vivo. ORC1 is subsequently recruited to chromatin for licensing and activation of early replication origins. Depletion of H2A.Z results in defects of DNA replication and cell proliferation in both HeLa cells and T cells. Thus, our results provide novel mechanistic insights that the histone variant H2A.Z epigenetically regulates licensing and activation of the early DNA replication origins through the Suv420H1-H4K20me2-ORC1 pathway. We first analyzed the interaction among H2A.Z, H4K20me2, ORC1, then investigated the role of H2A.Z on DNA replication through this pathway.