Balancing acts of two HEAT subunits of condensin I support dynamic assembly of chromosome axes

Dev Cell. 2015 Apr 6;33(1):94-106. doi: 10.1016/j.devcel.2015.01.034.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine Triphosphatases / genetics
  • Adenosine Triphosphatases / metabolism*
  • Adenosine Triphosphate / metabolism
  • Animals
  • Binding Sites
  • Chromosome Segregation
  • Chromosomes / chemistry*
  • Chromosomes / genetics
  • Chromosomes / metabolism*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Female
  • Fluorescent Antibody Technique
  • Immunoprecipitation
  • Mitosis / physiology*
  • Multiprotein Complexes / genetics
  • Multiprotein Complexes / metabolism*
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism*
  • Protein Subunits
  • Xenopus laevis / genetics*
  • Xenopus laevis / growth & development
  • Xenopus laevis / metabolism


  • DNA-Binding Proteins
  • Multiprotein Complexes
  • Nuclear Proteins
  • Protein Subunits
  • condensin complexes
  • Adenosine Triphosphate
  • Adenosine Triphosphatases