Protein phosphatase 1 recruitment by Rif1 regulates DNA replication origin firing by counteracting DDK activity

The eukaryotic genome is replicated according to a strict temporal program. Here, Bianchi and colleagues find that Rif1, a master regulator of the DNA replication program in yeast and mammals, exerts its effect on DNA replication origins by recruiting protein phosphatase 1 (PP1) to chromosomes. Rif1/PP1 counteracts the positive action of the DDK kinase on the replicative kinase MCM. In a final twist, kinase action on Rif1 is proposed to eventually release PP1 and allow origin firing.