Requirement of chromatid cohesion proteins rad21/scc1 and mis4/scc2 for normal spindle-kinetochore interaction in fission yeast.
BACKGROUND
Proteins conserved from yeast to human hold two sister chromatids together. The failure to form cohesion in the S phase results in premature separation of chromatids in G2/M. Mitotic kinetochores free from microtubules or the lack of tension are known to activate spindle checkpoint.


RESULTS
The loss of chromatid cohesion in fission yeast mutants (mis4-242 and rad21-K1) leads to the activation of Mad2- and Bub1-dependent checkpoint, possibly due to a diminished microtubule-kinetochore interaction. Bub1, a checkpoint kinase, localizes briefly at early mitotic kinetochores in wild-type, whereas the cohesion mutation greatly increases the duration of kinetochore localization. Bub1 is bound to the central centromere region of mitotic cells. These cohesion mutants are hypersensitive to a tubulin poison and are synthetic lethal with dis1 and bir1/cut17, which are defective in microtubule-kinetochore interaction. The formation of specialized centromere chromatin containing CENP-A does not require cohesion. Dominant-negative noncleavable Rad21 fails to activate checkpoint but blocks sister chromatid separation and full spindle elongation in anaphase.


CONCLUSIONS
Mis4 and Rad21 (budding yeast Scc2 and Scc1 homologs, respectively) act in establishing the normal spindle-kinetochore interaction in early mitosis and inhibit sister chromatid separation until the cleavage of Rad21 in anaphase. Checkpoint directly or indirectly monitors the states of cohesion in early mitosis. Full spindle extension occurs with unequal nuclear division in cohesion mutants in the absence of Mad2.
Toyoda
Yusuke
Y
Department of Gene Mechanisms, Graduate School of Biostudies, 606-8502, Kyoto, Japan.
Furuya
Kanji
K
Goshima
Gohta
G
Nagao
Koji
K
Takahashi
Kohta
K
Yanagida
Mitsuhiro
M
D002453:Cell Cycle; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002842:Chromatids / Q000378:metabolism; D004268:DNA-Binding Proteins; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal; D049452:Green Fluorescent Proteins; D018386:Kinetochores / Q000378:metabolism; D008164:Luminescent Proteins / Q000378:metabolism; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010750:Phosphoproteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D012568:Schizosaccharomyces / Q000235:genetics / Q000378:metabolism* / Q000648:ultrastructure; D029702:Schizosaccharomyces pombe Proteins; D008941:Spindle Apparatus / Q000378:metabolism; D013696:Temperature
D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D008164:Luminescent Proteins; C115842:MIS4 protein, S pombe; D009687:Nuclear Proteins; D010750:Phosphoproteins; C429022:RAD21 protein, human; C092957:Rad21 protein, S pombe; D011993:Recombinant Fusion Proteins; D029702:Schizosaccharomyces pombe Proteins; D049452:Green Fluorescent Proteins