title: Rif1 controls DNA replication by directing Protein Phosphatase 1 to reverse Cdc7-mediated phosphorylation of the MCM complex.
abstract: 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.
authors.affiliation: Institute of Medical Sciences, University of Aberdeen, Foresterhill, Aberdeen AB25 2ZD, United Kingdom;
authors.forename: Shin-Ichiro
authors.initials: S
authors.lastname: Hiraga
authors.forename: Gina M
authors.initials: GM
authors.lastname: Alvino
authors.forename: Fujung
authors.initials: F
authors.lastname: Chang
authors.forename: Hui-Yong
authors.initials: HY
authors.lastname: Lian
authors.forename: Akila
authors.initials: A
authors.lastname: Sridhar
authors.forename: Takashi
authors.initials: T
authors.lastname: Kubota
authors.forename: Bonita J
authors.initials: BJ
authors.lastname: Brewer
authors.forename: Michael
authors.initials: M
authors.lastname: Weinreich
authors.forename: M K
authors.initials: MK
authors.lastname: Raghuraman
authors.forename: Anne D
authors.initials: AD
authors.lastname: Donaldson
mesh_terms: D018797:Cell Cycle Proteins / Q000378:metabolism*; D004261:DNA Replication / Q000235:genetics / Q000502:physiology*; D064110:Minichromosome Maintenance Proteins / Q000378:metabolism*; D009154:Mutation; D010766:Phosphorylation; D054645:Protein Phosphatase 1 / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism*; D034501:Telomere-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D013696:Temperature
chemical_list: D018797:Cell Cycle Proteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D034501:Telomere-Binding Proteins; C074461:RIF1 protein, S cerevisiae; C489404:CDC7 protein, S cerevisiae; D017346:Protein Serine-Threonine Kinases; D054645:Protein Phosphatase 1; D064110:Minichromosome Maintenance Proteins
keywords: DNA replication; PP1; protein kinase; protein phosphatase; protein phosphorylation