title: CDK-dependent potentiation of MPS1 kinase activity is essential to the mitotic checkpoint.
abstract: Accurate chromosome segregation relies upon a mitotic checkpoint that monitors kinetochore attachment toward opposite spindle poles before enabling chromosome disjunction [1]. The MPS1/TTK protein kinase is a core component of the mitotic checkpoint that lies upstream of MAD2 and BubR1 both at the kinetochore and in the cytoplasm [2, 3]. To gain insight into the mechanisms underlying the regulation of MPS1 kinase, we undertook the identification of Xenopus MPS1 phosphorylation sites by mass spectrometry. We mapped several phosphorylation sites onto MPS1 and we show that phosphorylation of S283 in the noncatalytic region of MPS1 is required for full kinase activity. This phosphorylation potentiates MPS1 catalytic efficiency without impairing its affinity for the substrates. By using Xenopus egg extracts depleted of endogenous MPS1 and reconstituted with single point mutants, we show that phosphorylation of S283 is essential to activate the mitotic checkpoint. This phosphorylation does not regulate the localization of MPS1 to the kinetochore but is required for the recruitment of MAD1/MAD2, demonstrating its role at the kinetochore. Constitutive phosphorylation of S283 lowers the number of kinetochores required to hold the checkpoint, which suggests that CDK-dependent phosphorylation of MPS1 is essential to sustain the mitotic checkpoint when few kinetochores remain unattached.
authors.affiliation: Université Montpellier, CRBM, 34293 Montpellier, France.
authors.forename: Violeta
authors.initials: V
authors.lastname: Morin
authors.forename: Susana
authors.initials: S
authors.lastname: Prieto
authors.forename: Sabrina
authors.initials: S
authors.lastname: Melines
authors.forename: Sonia
authors.initials: S
authors.lastname: Hem
authors.forename: Michel
authors.initials: M
authors.lastname: Rossignol
authors.forename: Thierry
authors.initials: T
authors.lastname: Lorca
authors.forename: Julien
authors.initials: J
authors.lastname: Espeut
authors.forename: Nathalie
authors.initials: N
authors.lastname: Morin
authors.forename: Ariane
authors.initials: A
authors.lastname: Abrieu
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D018844:Cyclin-Dependent Kinases / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D005455:Fluorescent Antibody Technique; D015151:Immunoblotting; D018386:Kinetochores / Q000378:metabolism*; D059566:M Phase Cell Cycle Checkpoints; D013058:Mass Spectrometry; D010063:Ovum / Q000378:metabolism; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D014981:Xenopus / Q000235:genetics / Q000378:metabolism*; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; C499480:Mad2 protein, Xenopus; D014157:Transcription Factors; D029867:Xenopus Proteins; D017346:Protein Serine-Threonine Kinases; C514980:RPS27 protein, Xenopus; D018844:Cyclin-Dependent Kinases