Stable kinetochore-microtubule interactions depend on the Ska complex and its new component Ska3/C13Orf3.
Ska1 and Ska2 form a complex at the kinetochore-microtubule (KT-MT) interface and are required for timely progression from metaphase to anaphase. Here, we use mass spectrometry to search for additional components of the Ska complex. We identify C13Orf3 (now termed Ska3) as a novel member of this complex and map the interaction domains among the three known components. Ska3 displays similar characteristics as Ska1 and Ska2: it localizes to the spindle and KT throughout mitosis and its depletion markedly delays anaphase transition. Interestingly, a more complete removal of the Ska complex by concomitant depletion of Ska1 and Ska3 results in a chromosome congression failure followed by cell death. This severe phenotype reflects a destabilization of KT-MT interactions, as demonstrated by reduced cold stability of KT fibres. Yet, the depletion of the Ska complex only marginally impairs KT localization of the KMN network responsible for MT attachment. We propose that the Ska complex functionally complements the KMN, providing an additional layer of stability to KT-MT attachment and possibly signalling completion of attachment to the spindle checkpoint.
Gaitanos
Thomas N
TN
Department of Cell Biology, Max Planck Institute of Biochemistry, Martinsried, Germany.
Santamaria
Anna
A
Jeyaprakash
A Arockia
AA
Wang
Bin
B
Conti
Elena
E
Nigg
Erich A
EA
D018797:Cell Cycle Proteins; D002468:Cell Physiological Phenomena; D002868:Chromosomal Proteins, Non-Histone / Q000378:metabolism; D020090:Chromosome Segregation; D048749:Cytokinesis; D006367:HeLa Cells; D006801:Humans; D018386:Kinetochores / Q000378:metabolism*; D008869:Microtubule-Associated Proteins / Q000378:metabolism*; D008870:Microtubules / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping
D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D008869:Microtubule-Associated Proteins; C516427:SKA1 protein, human; C516428:SKA2 protein, human; C541140:Ska3 protein, human