title: v-Src-induced nuclear localization of YAP is involved in multipolar spindle formation in tetraploid cells.
abstract: The protein-tyrosine kinase, c-Src, is involved in a variety of signaling events, including cell division. We have reported that v-Src, which is a mutant variant of the cellular proto-oncogene, c-Src, causes delocalization of Aurora B kinase, resulting in a furrow regression in cytokinesis and the generation of multinucleated cells. However, the effect of v-Src on mitotic spindle formation is unknown. Here we show that v-Src-expressing HCT116 and NIH3T3 cells undergo abnormal cell division, in which cells separate into more than two cells. Upon v-Src expression, the proportion of multinucleated cells is increased in a time-dependent manner. Flow cytometry analysis revealed that v-Src increases the number of cells having a ≥4N DNA content. Microscopic analysis showed that v-Src induces the formation of multipolar spindles with excess centrosomes. These results suggest that v-Src induces multipolar spindle formation by generating multinucleated cells. Tetraploidy activates the tetraploidy checkpoint, leading to a cell cycle arrest of tetraploid cells at the G1 phase, in which the nuclear exclusion of the transcription co-activator YAP plays a critical role. In multinucleated cells that are induced by cytochalasin B and the Plk1 inhibitor, YAP is excluded from the nucleus. However, v-Src prevents this nuclear exclusion of YAP through a decrease in the phosphorylation of YAP at Ser127 in multinucleated cells. Furthermore, v-Src decreases the expression level of p53, which also plays a critical role in the cell cycle arrest of tetraploid cells. These results suggest that v-Src promotes abnormal spindle formation in at least two ways: generation of multinucleated cells and a weakening of the tetraploidy checkpoint.
authors.affiliation: Department of Biochemistry & Molecular Biology, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
authors.forename: Keiko
authors.initials: K
authors.lastname: Kakae
authors.affiliation: Department of Biochemistry & Molecular Biology, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
authors.forename: Masayoshi
authors.initials: M
authors.lastname: Ikeuchi
authors.affiliation: Department of Biochemistry & Molecular Biology, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
authors.forename: Takahisa
authors.initials: T
authors.lastname: Kuga
authors.affiliation: Department of Biochemistry & Molecular Biology, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan.
authors.forename: Youhei
authors.initials: Y
authors.lastname: Saito
authors.affiliation: Laboratory of Molecular Cell Biology, Graduate School of Pharmaceutical Sciences, Chiba University, Chiba 260-8675, Japan.
authors.forename: Naoto
authors.initials: N
authors.lastname: Yamaguchi
authors.affiliation: Department of Biochemistry & Molecular Biology, Kyoto Pharmaceutical University, Kyoto 607-8414, Japan. Electronic address: nakayama@mb.kyoto-phu.ac.jp.
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakayama
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins; D002455:Cell Division; D002467:Cell Nucleus / Q000378:metabolism*; D018385:Centrosome / Q000378:metabolism; D004247:DNA / Q000378:metabolism; D015726:Giant Cells / Q000166:cytology / Q000378:metabolism; D045325:HCT116 Cells; D006801:Humans; D051379:Mice; D041681:NIH 3T3 Cells; D015688:Oncogene Protein pp60(v-src) / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D021381:Protein Transport; D000090063:Proto-Oncogene Mas; D008941:Spindle Apparatus / Q000378:metabolism*; D057891:Tetraploidy; D013997:Time Factors; D000091102:YAP-Signaling Proteins
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; C000715470:MAS1 protein, human; D010750:Phosphoproteins; D000090063:Proto-Oncogene Mas; D000091102:YAP-Signaling Proteins; C486223:Yap1 protein, mouse; D004247:DNA; D015688:Oncogene Protein pp60(v-src)
keywords: Multipolar spindle; Tetraploidy checkpoint; YAP; v-Src