The Saccharomyces cerevisiae spindle pole body duplication gene MPS1 is part of a mitotic checkpoint.
M-phase checkpoints inhibit cell division when mitotic spindle function is perturbed. Here we show that the Saccharomyces cerevisiae MPS1 gene product, an essential protein kinase required for spindle pole body (SPB) duplication (Winey et al., 1991; Lauze et al., 1995), is also required for M-phase check-point function. In cdc31-2 and mps2-1 mutants, conditional failure of SPB duplication results in cell cycle arrest with high p34CDC28 kinase activity that depends on the presence of the wild-type MAD1 checkpoint gene, consistent with checkpoint arrest of mitosis. In contrast, mps1 mutant cells fail to duplicate their SPBs and do not arrest division at 37 degrees C, exhibiting a normal cycle of p34CDC28 kinase activity despite the presence of a monopolar spindle. Double mutant cdc31-2, mps1-1 cells also fail to arrest mitosis at 37 degrees C, despite having SPB structures similar to cdc31-2 single mutants as determined by EM analysis. Arrest of mitosis upon microtubule depolymerization by nocodazole is also conditionally absent in mps1 strains. This is observed in mps1 cells synchronized in S phase with hydroxyurea before exposure to nocodazole, indicating that failure of checkpoint function in mps1 cells is independent of SPB duplication failure. In contrast, hydroxyurea arrest and a number of other cdc mutant arrest phenotypes are unaffected by mps1 alleles. We propose that the essential MPS1 protein kinase functions both in SPB duplication and in a mitotic checkpoint monitoring spindle integrity.
Weiss
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Department of Molecular, Cellular, and Developmental Biology, University of Colorado-Boulder 80309-0347, USA.
Winey
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D017489:CDC28 Protein Kinase, S cerevisiae / Q000235:genetics / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism; D002352:Carrier Proteins; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D006918:Hydroxyurea / Q000494:pharmacology; D016200:Maturation-Promoting Factor / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects / Q000235:genetics*; D015739:Nocodazole / Q000494:pharmacology; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism; D011494:Protein Kinases; D017346:Protein Serine-Threonine Kinases / Q000235:genetics*; D011505:Protein-Tyrosine Kinases / Q000235:genetics*; D012097:Repressor Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins; D008941:Spindle Apparatus / Q000235:genetics*
C083769:CDC31 protein, S cerevisiae; D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; C501382:MAD1 protein, S cerevisiae; C501384:MAD1L1 protein, human; D009687:Nuclear Proteins; D010750:Phosphoproteins; D012097:Repressor Proteins; D029701:Saccharomyces cerevisiae Proteins; D011494:Protein Kinases; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D017489:CDC28 Protein Kinase, S cerevisiae; D016200:Maturation-Promoting Factor; C075840:TTK protein, human; C093416:MPS1 protein, S cerevisiae; D015739:Nocodazole; D006918:Hydroxyurea