MPS1/Mph1 phosphorylates the kinetochore protein KNL1/Spc7 to recruit SAC components.
The genomic stability of all organisms depends on the precise partition of chromosomes to daughter cells. The spindle assembly checkpoint (SAC) senses unattached kinetochores and prevents premature entry to anaphase, thus ensuring that all chromosomes attach to opposite spindle poles (bi-orientation) during mitosis. MPS1 is an evolutionarily conserved protein kinase required for the SAC and chromosome bi-orientation. Yet, its primary cellular substrate has remained elusive. We show that fission yeast Mph1 (MPS1 homologue) phosphorylates the kinetochore protein Spc7 (KNL1/Blinkin homologue) at the MELT repeat sequences. This phosphorylation promotes the in vitro binding to the Bub1-Bub3 complex, which is required for kinetochore-based SAC activation (Mad1-Mad2-Mad3 localization) and chromosome alignment. Accordingly, a non-phosphorylatable spc7-12A mutation abolishes kinetochore targeting of Bub1-Bub3, whereas a phospho-mimetic spc7-12E mutation forces them to localize at kinetochores throughout the entire cell cycle, even in the absence of Mph1. Thus, MPS1/Mph1 kinase locating at the unattached kinetochores initially creates a mark, which is crucial for SAC activation and chromosome bi-orientation. This mechanism seems to be conserved in human cells.
Laboratory of Chromosome Dynamics, Institute of Molecular and Cellular Biosciences, University of Tokyo, Yayoi, Tokyo 113-0032, Japan.
Yuya
Y
Yamagishi
Ching-Hui
CH
Yang
Yuji
Y
Tanno
Yoshinori
Y
Watanabe
D018797:Cell Cycle Proteins / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism*; D020090:Chromosome Segregation; D018386:Kinetochores / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints; D064246:Mad2 Proteins; D009154:Mutation; D009687:Nuclear Proteins / Q000378:metabolism; D010766:Phosphorylation; D011485:Protein Binding; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D013997:Time Factors
C544653:Bub3 protein, S pombe; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; C500242:Spc7 protein, S pombe; C501383:mad1 protein, S pombe; C577696:mad2 protein, S pombe; C512748:mad3 protein, S pombe; C570446:Mph1 protein, S pombe; D011494:Protein Kinases; C495594:Bub1 protein, S pombe; D017346:Protein Serine-Threonine Kinases