title: Balancing acts of two HEAT subunits of condensin I support dynamic assembly of chromosome axes.
abstract: Condensin I is a five-subunit protein complex that plays a central role in mitotic chromosome assembly and segregation in eukaryotes. To dissect its mechanism of action, we reconstituted wild-type and mutant complexes from recombinant subunits and tested their abilities to assemble chromosomes in Xenopus egg cell-free extracts depleted of endogenous condensins. We find that ATP binding and hydrolysis by SMC subunits have distinct contributions to the action of condensin I and that continuous ATP hydrolysis is required for structural maintenance of chromosomes. Mutant complexes lacking either one of two HEAT subunits produce abnormal chromosomes with highly characteristic defects and have contrasting structural effects on chromosome axes preassembled with the wild-type complex. We propose that balancing acts of the two HEAT subunits support dynamic assembly of chromosome axes under the control of the SMC ATPase cycle, thereby governing construction of rod-shaped chromosomes in eukaryotic cells.
authors: Chromosome Dynamics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan.
authors: Kazuhisa
authors: K
authors: Kinoshita
authors: Institute of Industrial Sciences, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
authors: Tetsuya J
authors: TJ
authors: Kobayashi
authors: Chromosome Dynamics Laboratory, RIKEN, 2-1 Hirosawa, Wako, Saitama 351-0198, Japan. Electronic address: hiranot@riken.jp.
authors: Tatsuya
authors: T
authors: Hirano
mesh_terms: D000251:Adenosine Triphosphatases / Q000235:genetics / Q000378:metabolism*; D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D001665:Binding Sites; D020090:Chromosome Segregation; D002875:Chromosomes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D005455:Fluorescent Antibody Technique; D047468:Immunoprecipitation; D008938:Mitosis / Q000502:physiology*; D046912:Multiprotein Complexes / Q000235:genetics / Q000378:metabolism*; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D014982:Xenopus laevis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D046912:Multiprotein Complexes; D009687:Nuclear Proteins; D021122:Protein Subunits; C108312:condensin complexes; D000255:Adenosine Triphosphate; D000251:Adenosine Triphosphatases