The vertebrate Ndc80 complex contains Spc24 and Spc25 homologs, which are required to establish and maintain kinetochore-microtubule attachment

Curr Biol. 2004 Jan 20;14(2):131-7. doi: 10.1016/j.cub.2003.12.058.


How kinetochores bind to microtubules and move on the mitotic spindle remain unanswered questions. Multiple systems have implicated the Ndc80/Hec1 (Ndc80) kinetochore complex in kinetochore-microtubule interaction and spindle checkpoint activity. In budding yeast, Ndc80 copurifies with three additional interacting proteins: Nuf2, Spc24, and Spc25. Although functional vertebrate homologs of Ndc80 and Nuf2 exist, extensive sequence similarity searches have not uncovered homologs of Spc24 and Spc25. We have purified the xNdc80 complex to homogeneity from Xenopus egg extracts and identified two novel interacting proteins. Although the sequences have greatly diverged, we have concluded that these are the functional homologs of the yeast Spc24 and Spc25 proteins based on limited sequence similarity, common coiled-coil domains, kinetochore localization, similar phenotypes, and copurification with xNdc80 and xNuf2. Using both RNAi and antibody injection experiments, we have extended previous characterization of the complex and found that Spc24 and Spc25 are required not only to establish, but also to maintain kinetochore-microtubule attachments and metaphase alignment. In addition, we show that Spc24 and Spc25 are required for chromosomal movement to the spindle poles in anaphase.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Anaphase / physiology
  • Animals
  • Base Sequence
  • Cytoskeletal Proteins
  • Kinetochores / metabolism*
  • Mass Spectrometry
  • Microscopy, Fluorescence
  • Microtubule-Associated Proteins / genetics*
  • Microtubule-Associated Proteins / metabolism*
  • Microtubules / metabolism*
  • Molecular Sequence Data
  • Nuclear Proteins / genetics
  • Nuclear Proteins / metabolism
  • Precipitin Tests
  • RNA Interference
  • Xenopus / genetics


  • Cytoskeletal Proteins
  • Microtubule-Associated Proteins
  • NDC80 protein, human
  • Nuclear Proteins

Associated data

  • GENBANK/AY456385
  • GENBANK/AY456386
  • GENBANK/AY456387
  • GENBANK/AY456388