title: Regulation of mitotic inhibitor Mik1 helps to enforce the DNA damage checkpoint.
abstract: The protein kinase Chk1 enforces the DNA damage checkpoint. This checkpoint delays mitosis until damaged DNA is repaired. Chk1 regulates the activity and localization of Cdc25, the tyrosine phosphatase that activates the cdk Cdc2. Here we report that Mik1, a tyrosine kinase that inhibits Cdc2, is positively regulated by the DNA damage checkpoint. Mik1 is required for checkpoint response in strains that lack Cdc25. Long-term DNA damage checkpoint arrest fails in Deltamik1 cells. DNA damage increases Mik1 abundance in a Chk1-dependent manner. Ubiquitinated Mik1 accumulates in a proteasome mutant, which indicates that Mik1 normally has a short half-life. Thus, the DNA damage checkpoint might regulate Mik1 degradation. Mik1 protein and mRNA oscillate during the unperturbed cell cycle, with peak amounts detected around S phase. These data indicate that regulation of Mik1 abundance helps to couple mitotic onset to the completion of DNA replication and repair. Coordinated negative regulation of Cdc25 and positive regulation of Mik1 ensure the effective operation of the DNA damage checkpoint.
authors.affiliation: Departments of Molecular Biology and Cell Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Baber-Furnari
authors.forename: N
authors.initials: N
authors.lastname: Rhind
authors.forename: M N
authors.initials: MN
authors.lastname: Boddy
authors.forename: P
authors.initials: P
authors.lastname: Shanahan
authors.forename: A
authors.initials: A
authors.lastname: Lopez-Girona
authors.forename: P
authors.initials: P
authors.lastname: Russell
mesh_terms: D016203:CDC2 Protein Kinase / Q000378:metabolism; D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism; D000071877:Checkpoint Kinase 1; D003546:Cysteine Endopeptidases; D004249:DNA Damage; D004261:DNA Replication; D004271:DNA, Fungal / Q000096:biosynthesis; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D016195:G2 Phase; D005982:Glutathione Transferase / Q000235:genetics / Q000378:metabolism; D008938:Mitosis; D009097:Multienzyme Complexes; D016296:Mutagenesis; D046988:Proteasome Endopeptidase Complex; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012568:Schizosaccharomyces; D029702:Schizosaccharomyces pombe Proteins; D015398:Signal Transduction; D014452:Ubiquitins / Q000378:metabolism; D020666:ras-GRF1 / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D005656:Fungal Proteins; D009097:Multienzyme Complexes; D012333:RNA, Messenger; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; D014452:Ubiquitins; D020666:ras-GRF1; D005982:Glutathione Transferase; D011494:Protein Kinases; C090679:mik1 protein, S pombe; D011505:Protein-Tyrosine Kinases; D000071877:Checkpoint Kinase 1; C000605873:Chk1 protein, S pombe; D016203:CDC2 Protein Kinase; D003546:Cysteine Endopeptidases; D046988:Proteasome Endopeptidase Complex