title: Two LXXLL motifs in the N terminus of Mps1 are required for Mps1 nuclear import during G(2)/M transition and sustained spindle checkpoint responses.
abstract: Spindle assembly checkpoint kinase Mps1 is spatially and temporally regulated during cell cycle progression. Mps1 is predominately localized to the cytosol in interphase cells, whereas it is concentrated on kinetochores in prophase and prometaphase cells. The timing and mechanism of Mps1 redistribution during cell cycle transition is currently poorly understood. Here, we show that Mps1 relocates from the cytosol to the nucleus at the G 2/M boundary prior to nuclear envelope breakdown (NEB). This timely translocation depends on two tandem LXXLL motifs in the N terminus of Mps1, and mutations in either motif abolish Mps1 nuclear accumulation. Furthermore, we found that phosphorylation of Mps1 Ser80 (which is located between the two LXXLL motifs) also plays a role in regulating timely nuclear entry of Mps1. Mps1 that is defective in LXXLL motifs has near wild-type kinase activity. Moreover, the kinase activity of Mps1 appears to be dispensable for nuclear translocation, as inhibition of Mps1 by a highly specific small-molecule inhibitor did not perturb its nuclear entry. Remarkably, translocation-deficient Mps1 can mediate activation of spindle assembly checkpoint response; however, it fails to support a sustained mitotic arrest upon prolonged treatment with nocodazole. The mitotic slippage can be attributed to precocious degradation of Mps1 in the arrested cells. Our studies reveal a novel cell cycle-dependent nuclear translocation signal in the N terminus of Mps1 and suggest that timely nuclear entry could be important for sustaining spindle assembly checkpoint responses.
authors.affiliation: University of Colorado at Boulder, Boulder, CO, USA.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zhang
authors.forename: Qingqing
authors.initials: Q
authors.lastname: Yin
authors.forename: Youguo
authors.initials: Y
authors.lastname: Ling
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Zhang
authors.forename: Runlin
authors.initials: R
authors.lastname: Ma
authors.forename: Qingjun
authors.initials: Q
authors.lastname: Ma
authors.forename: Cheng
authors.initials: C
authors.lastname: Cao
authors.forename: Hui
authors.initials: H
authors.lastname: Zhong
authors.forename: Xuedong
authors.initials: X
authors.lastname: Liu
authors.forename: Quanbin
authors.initials: Q
authors.lastname: Xu
mesh_terms: D021581:Active Transport, Cell Nucleus; D020816:Amino Acid Motifs / Q000235:genetics; D018797:Cell Cycle Proteins / Q000235:genetics* / Q000378:metabolism*; D002455:Cell Division; D045744:Cell Line, Tumor; D020090:Chromosome Segregation / Q000187:drug effects; D016195:G2 Phase; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins / Q000235:genetics*; D018386:Kinetochores; D059566:M Phase Cell Cycle Checkpoints; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism*; D011804:Quinolines / Q000494:pharmacology; D034622:RNA Interference; D034741:RNA, Small Interfering; D015398:Signal Transduction; D008941:Spindle Apparatus / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D013844:Thiazoles / Q000494:pharmacology
chemical_list: D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D011804:Quinolines; D034741:RNA, Small Interfering; C512984:RO 3306; D013844:Thiazoles; D011505:Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; C075840:TTK protein, human