Spindle checkpoint signaling requires the mis6 kinetochore subcomplex, which interacts with mad2 and mitotic spindles.
The spindle checkpoint coordinates cell cycle progression and chromosome segregation by inhibiting anaphase promoting complex/cyclosome until all kinetochores interact with the spindle properly. During early mitosis, the spindle checkpoint proteins, such as Mad2 and Bub1, accumulate at kinetochores that do not associate with the spindle. Here, we assess the requirement of various kinetochore components for the accumulation of Mad2 and Bub1 on the kinetochore in fission yeast and show that the necessity of the Mis6-complex and the Nuf2-complex is an evolutionarily conserved feature in the loading of Mad2 onto the kinetochore. Furthermore, we demonstrated that Nuf2 is required for maintaining the Mis6-complex on the kinetochore during mitosis. The Mis6-complex physically interacts with Mad2 under the condition that the Mad2-dependent checkpoint is activated. Ectopically expressed N-terminal fragments of Mis6 localize along the mitotic spindle, highlighting the potential binding ability of Mis6 not only to the centromeric chromatin but also to the spindle microtubules. We propose that the Mis6-complex, in collaboration with the Nuf2-complex, monitors the spindle-kinetochore attachment state and acts as a platform for Mad2 to accumulate at unattached kinetochores.
Saitoh
Shigeaki
S
Division of Cell Biology, Institute of Life Science, Kurume University, Fukuoka 839-0864, Japan.
Ishii
Kojiro
K
Kobayashi
Yasuyo
Y
Takahashi
Kohta
K
D001324:Autoantigens / Q000378:metabolism; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D000076247:Centromere Protein A; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D018386:Kinetochores / Q000378:metabolism*; D064246:Mad2 Proteins; D008938:Mitosis; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029702:Schizosaccharomyces pombe Proteins / Q000235:genetics / Q000378:metabolism*; D008941:Spindle Apparatus / Q000378:metabolism*
D001324:Autoantigens; D018797:Cell Cycle Proteins; D000076247:Centromere Protein A; D002868:Chromosomal Proteins, Non-Histone; D064246:Mad2 Proteins; C107314:Mis6 protein, S pombe; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; C577696:mad2 protein, S pombe; C492315:mis12 protein, S pombe; C490196:nuf2 protein, S pombe; C495594:Bub1 protein, S pombe; D017346:Protein Serine-Threonine Kinases