PROTEIN-KINASE INHIBITION IN G2 CAUSES MAMMALIAN MOM PROTEINS TO REASSOCIATE WITH CHROMATIN AND RESTORES ABILITY TO REPLICATE

Intact nuclei from G2-phase mammalian cells will replicate their DNA i n Xenopus egg extract if they are preexposed to the protein kinase inh ibitor 6-dimethy-laminopurine in vivo (Coverley et al., Exp. Cell Res. 225, 294-300, 1996). Here, we demonstrate that this competence to rer eplicate is accompanied by alterations in the subcellular distribution of the Mcm family of proteins, which are implicated in replication li censing (Hennessy et al., Genes Dev. 4, 2252-2263, 1990; Kubota et al. , Cell 81, 601-609, 1995; and Chong et al., Nature 375, 418-421, 1995) . All family members reassociate with chromatin in G2 cells and this c orrelates closely with regeneration of replication competence. Moreove r, newly bound Mcm proteins are functional for replication because, un like untreated Ga nuclei, replication of treated G2 nuclei in vitro oc curs independent of the Xenopus Mcm protein complex. These observation s show that the postreplicative state is actively maintained in G2 cel ls by a protein kinase(s) which regulates the behavior of Mcm family p roteins. (C) 1998 Academic Press.