Rif1 controls DNA replication by directing Protein Phosphatase 1 to reverse Cdc7-mediated phosphorylation of the MCM complex

• Published in: Genes & development Vol. 28; no. 4; pp. 372 - 383
• Main Authors: Hiraga, Shin-Ichiro, Alvino, Gina M, Chang, Fujung, Lian, Hui-Yong, Sridhar, Akila, Kubota, Takashi, Brewer, Bonita J, Weinreich, Michael, Raghuraman, M K, Donaldson, Anne D
• Format: Journal Article
• Language: English
• Published: United States Cold Spring Harbor Laboratory Press 15.02.2014
• Subjects: Cell Cycle Proteins - metabolism; DNA Replication - genetics; DNA Replication - physiology; Minichromosome Maintenance Proteins - metabolism; Mutation; Phosphorylation; Protein Phosphatase 1 - metabolism; Protein Serine-Threonine Kinases - metabolism; Protein Structure, Tertiary; Repressor Proteins - genetics; Repressor Proteins - metabolism; Research Paper; Saccharomyces cerevisiae; Saccharomyces cerevisiae - enzymology; Saccharomyces cerevisiae - genetics; Saccharomyces cerevisiae - metabolism; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Schizosaccharomyces pombe; Telomere-Binding Proteins - genetics; Telomere-Binding Proteins - metabolism; Temperature; PP1; DNA replication; protein phosphorylation; protein kinase; protein phosphatase
• ISSN: 0890-9369; 1549-5477
• DOI: 10.1101/gad.231258.113

Initiation of eukaryotic DNA replication requires phosphorylation of the MCM complex by Dbf4-dependent kinase (DDK), composed of Cdc7 kinase and its activator, Dbf4. We report here that budding yeast Rif1 (Rap1-interacting factor 1) controls DNA replication genome-wide and describe how Rif1 opposes DDK function by directing Protein Phosphatase 1 (PP1)-mediated dephosphorylation of the MCM complex. Deleting RIF1 partially compensates for the limited DDK activity in a cdc7-1 mutant strain by allowing increased, premature phosphorylation of Mcm4. PP1 interaction motifs within the Rif1 N-terminal domain are critical for its repressive effect on replication. We confirm that Rif1 interacts with PP1 and that PP1 prevents premature Mcm4 phosphorylation. Remarkably, our results suggest that replication repression by Rif1 is itself also DDK-regulated through phosphorylation near the PP1-interacting motifs. Based on our findings, we propose that Rif1 is a novel PP1 substrate targeting subunit that counteracts DDK-mediated phosphorylation during replication. Fission yeast and mammalian Rif1 proteins have also been implicated in regulating DNA replication. Since PP1 interaction sites are evolutionarily conserved within the Rif1 sequence, it is likely that replication control by Rif1 through PP1 is a conserved mechanism.