title: Analysis of Scc1-deficient cells defines a key metaphase role of vertebrate cohesin in linking sister kinetochores.
abstract: Cleavage of the cohesin subunit Scc1p/Mcd1p/Rad21 permits sister chromatid separation and is considered to trigger anaphase onset. It has also been suggested that the cohesin complex is essential for chromosome condensation and for assembling fully functional kinetochores. Here, we used vertebrate cells conditionally deficient in Scc1 to probe cohesin function in mitosis. Cells lacking cohesin arrest in prometaphase, with many chromosomes failing to align at a metaphase plate and high levels of the spindle assembly checkpoint protein, BubR1, at all kinetochores. We show that the structural integrity of chromosomes is normal in the absence of Scc1. Furthermore, specific inhibition of topoisomerase II, which is required for decatenation of replicated chromosomes, can bypass the cohesin requirement for metaphase chromosome alignment and spindle checkpoint silencing. Since the kinetochore effects of Scc1 deficiency can be compensated for by topoisomerase II inhibition, we conclude that Scc1 is not absolutely required for kinetochore assembly or function, and that its principal role in allowing the onset of anaphase is the establishment of sufficient inter-sister tension to allow biorientation.
authors.affiliation: Wellcome Trust Centre for Cell Biology, Institute of Cell and Molecular Biology, Swann Building, King's Buildings, University of Edinburgh, Mayfield Road, Edinburgh EH9 3JR, UK.
authors.forename: Paola
authors.initials: P
authors.lastname: Vagnarelli
authors.forename: Ciaran
authors.initials: C
authors.lastname: Morrison
authors.forename: Helen
authors.initials: H
authors.lastname: Dodson
authors.forename: Eiichiro
authors.initials: E
authors.lastname: Sonoda
authors.forename: Shunichi
authors.initials: S
authors.lastname: Takeda
authors.forename: William C
authors.initials: WC
authors.lastname: Earnshaw
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism; D000818:Animals; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics* / Q000378:metabolism; D002460:Cell Line; D002645:Chickens / Q000235:genetics / Q000378:metabolism; D002842:Chromatids / Q000235:genetics / Q000378:metabolism; D002868:Chromosomal Proteins, Non-Histone / Q000235:genetics / Q000378:metabolism; D002875:Chromosomes / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005656:Fungal Proteins; D017353:Gene Deletion; D018386:Kinetochores / Q000378:metabolism* / Q000648:ultrastructure; D008677:Metaphase / Q000235:genetics / Q000502:physiology*; D008856:Microscopy, Fluorescence; D008938:Mitosis / Q000235:genetics / Q000502:physiology; D046912:Multiprotein Complexes; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D010750:Phosphoproteins; D029701:Saccharomyces cerevisiae Proteins; D059005:Topoisomerase II Inhibitors; D014404:Tubulin / Q000235:genetics / Q000378:metabolism; D000097722:Cohesins
chemical_list: D000251:Adenosine Triphosphatases; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D010750:Phosphoproteins; D029701:Saccharomyces cerevisiae Proteins; D059005:Topoisomerase II Inhibitors; D014404:Tubulin; D000097722:Cohesins; C490529:MCD1 protein, S cerevisiae; C060905:centromere protein C; C108312:condensin complexes