Fission yeast Bub1 is essential in setting up the meiotic pattern of chromosome segregation.
In meiosis, sister-chromatids move to the same spindle pole during the first division (MI) and to opposite poles during the second division (MII). This requires that MI sister kinetochores are co-orientated and form an apparent single functional unit that only interacts with microtubules from one pole, and that sister-chromatids remain associated through their centromeres until anaphase II. Here we investigate the function of Bub1 and Mad2, which are components of the mitotic-spindle checkpoint, on chromosome segregation during meiosis. Both proteins are required to prevent the occurrence of non-disjunction events in MI, which is consistent with recent findings that components of the mitotic-spindle checkpoint also operate during meiosis. However, Bub1 has several functions that are not shared with Mad2. When the bub1 gene is deleted, sister chromatids often move to opposite spindle poles during MI, indicating that sister kinetochores are disunited. Furthermore, the cohesin Rec8 is never retained at centromeres at anaphase I and sister-chromatid cohesion is lost. Our results show that Bub1, besides its functions in monitoring chromosome attachment, is essential for two other significant aspects of MI - unification of sister kinetochores and retention of centromeric cohesion.
Bernard
P
P
Institut de Biochimie et Génétique Cellulaires, Centre National de la Recherche Scientifique, Unité Mixte de Recherche 5095, 1 Rue Camille Saint Saëns, 33077 Bordeaux, France.
Maure
J F
JF
Javerzat
J P
JP
D000705:Anaphase / Q000502:physiology; D002135:Calcium-Binding Proteins / Q000378:metabolism / Q000502:physiology; D002352:Carrier Proteins; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins; D002842:Chromatids / Q000378:metabolism*; D020090:Chromosome Segregation; D005656:Fungal Proteins / Q000378:metabolism / Q000502:physiology; D049452:Green Fluorescent Proteins; D017404:In Situ Hybridization, Fluorescence; D008164:Luminescent Proteins / Q000378:metabolism; D064246:Mad2 Proteins; D008540:Meiosis / Q000502:physiology; D008856:Microscopy, Fluorescence; D009687:Nuclear Proteins; D011494:Protein Kinases / Q000378:metabolism* / Q000502:physiology*; D017346:Protein Serine-Threonine Kinases; D012568:Schizosaccharomyces / Q000737:chemistry*; D029702:Schizosaccharomyces pombe Proteins
D002135:Calcium-Binding Proteins; D002352:Carrier Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D008164:Luminescent Proteins; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029702:Schizosaccharomyces pombe Proteins; C577696:mad2 protein, S pombe; D049452:Green Fluorescent Proteins; D011494:Protein Kinases; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases