title: Stability of kinetochore-microtubule attachment and the role of different KMN network components in Drosophila.
abstract: Kinetochores bind spindle microtubules and also act as signaling centers that monitor this interaction. Defects in kinetochore assembly lead to chromosome missegregation and aneuploidy. The interaction between microtubules and chromosomes involves a conserved super-complex of proteins, known as the KNL1Mis12Ndc80 (KMN) network, composed by the KNL1 (Spc105), Mis12, and Ndc80 complexes. Previous studies indicate that all components of the network are required for kinetochore-microtubule attachment and all play relevant functions in chromosome congression, biorientation, and segregation. Here, we report a comparative study addressing the role of the different KMN components using dsRNA and in vivo fluorescence microscopy in Drosophila S2 cells allowing us to suggest that different KMN network components might perform different roles in chromosome segregation and the mitotic checkpoint signaling. Depletion of different components results in mostly lateral kinetochore-microtubule attachments that are relatively stable on depletion of Mis12 or Ndc80 but very unstable after Spc105 depletion. In vivo analysis on depletion of Mis12, Ndc80, and to some extent Spc105, shows that lateral kinetochore-microtubule interactions are still functional allowing poleward kinetochore movement. We also find that different KMN network components affect differently the localization of spindle assembly checkpoint (SAC) proteins at kinetochores. Depletion of Ndc80 and Spc105 abolishes the mitotic checkpoint, whereas depletion of Mis12 causes a delay in mitotic progression. Taken together, our results suggest that Mis12 and Ndc80 complexes help to properly orient microtubule attachment, whereas Spc105 plays a predominant role in the kinetochore-microtubule attachment as well as in the poleward movement of chromosomes, SAC response, and cell viability.
authors: IBMC, Instituto de Biologia Molecular e Celular, Molecular Genetics, Universidade do Porto, Rua do Campo Alegre 823, 4150-180, Porto, Portugal.
authors: Tália
authors: T
authors: Feijão
authors: Olga
authors: O
authors: Afonso
authors: André F
authors: AF
authors: Maia
authors: Claudio E
authors: CE
authors: Sunkel
mesh_terms: D000818:Animals; D020090:Chromosome Segregation; D029721:Drosophila Proteins / Q000378:metabolism*; D004331:Drosophila melanogaster / Q000166:cytology / Q000378:metabolism*; D018386:Kinetochores / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D008938:Mitosis; D046912:Multiprotein Complexes / Q000378:metabolism*; D034622:RNA Interference
chemical_list: D029721:Drosophila Proteins; D046912:Multiprotein Complexes
keywords: Drosophila; KMN network; kinetochores; microtubules; mitosis