title: Role of the Mad2 dimerization interface in the spindle assembly checkpoint independent of kinetochores.
abstract: BACKGROUND
  The spindle assembly checkpoint (SAC) arrests cells when kinetochores are unattached to spindle microtubules. The signaling pathway is initiated at the kinetochores by one SAC component, Mad2, which catalyzes the initial steps of the cascade via the conformational dimerization of its open and closed conformers. Away from kinetochores, the dimerization surface of Mad2 has been proposed, based on data in vitro, to either interact with SAC activators or inactivators and thus to contribute to SAC activation or silencing. Here, we analyze its role in vivo.
  
  
  RESULTS
  To analyze the putative pathway downstream of the kinetochores, we used two complementary approaches: we activated the SAC ectopically and independently from kinetochores, and we separated genetically the kinetochore-dependent and independent pools of Mad2. We found that the dimerization surface is required also downstream of kinetochores to mount a checkpoint response.
  
  
  CONCLUSIONS
  Our results show that away from kinetochores the dimerization surface is required for stabilizing the end-product of the pathway, the mitotic checkpoint complex. Surprisingly, downstream of kinetochores the surface does not mediate Mad2 dimerization. Instead, our results are consistent with a role of Mad3 as the main interactor of Mad2 via the dimerization surface.
authors.affiliation: IFOM, The FIRC Institute of Molecular Oncology, Via Adamello 16, 20139 Milan, Italy.
authors.forename: Luca
authors.initials: L
authors.lastname: Mariani
authors.forename: Elena
authors.initials: E
authors.lastname: Chiroli
authors.forename: Luigi
authors.initials: L
authors.lastname: Nezi
authors.forename: Heiko
authors.initials: H
authors.lastname: Muller
authors.forename: Simonetta
authors.initials: S
authors.lastname: Piatti
authors.forename: Andrea
authors.initials: A
authors.lastname: Musacchio
authors.forename: Andrea
authors.initials: A
authors.lastname: Ciliberto
mesh_terms: D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000378:metabolism*; D005686:Galactokinase / Q000235:genetics; D018386:Kinetochores / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints; D064246:Mad2 Proteins; D008677:Metaphase / Q000235:genetics; D008870:Microtubules / Q000378:metabolism; D008938:Mitosis; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D055503:Protein Multimerization; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000235:genetics / Q000378:metabolism
chemical_list: C577495:CDC20 protein, S cerevisiae; D064199:Cdc20 Proteins; D018797:Cell Cycle Proteins; C577695:MAD2 protein, S cerevisiae; C406764:MAD3 protein, S cerevisiae; D064246:Mad2 Proteins; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; C524219:GAL1 protein, S cerevisiae; D005686:Galactokinase