HBO1 histone acetylase is a coactivator of the replication licensing factor Cdt1.

HBO1 histone acetylase is important for DNA replication licensing. In human cells, HBO1 associates with replication origins specifically during the G1 phase of the cell cycle in a manner that depends on the replication licensing factor Cdt1, but is independent of the Cdt1 repressor Geminin. HBO1 directly interacts with Cdt1, and it enhances Cdt1-dependent rereplication. Thus, HBO1 plays a direct role at replication origins as a coactivator of the Cdt1 licensing factor. As HBO1 is also a transcriptional coactivator, it has the potential to integrate internal and external stimuli to coordinate transcriptional responses with initiation of DNA replication.