title: SIRT2 downregulation confers resistance to microtubule inhibitors by prolonging chronic mitotic arrest.
abstract: We previously identified SIRT2, a deacetylase for tubulin and histone H4, as a protein downregulated in gliomas, and reported that exogenously-expressed SIRT2 arrests the cell cycle prior to entry into mitosis to prevent chromosomal instability in response to microtubule inhibitors (MTIs) such as nocodazole, characteristics previously reported for the CHFR protein. We herein investigated the effects of SIRT2 downregulation on sensitivity to MTIs using HCT116 cells, a mitotic checkpoint-proficient near-diploid cancer cell line used for studying checkpoints. We found that SIRT2 downregulation confers resistance to MTIs as well as that of BubR1, a well-characterized mitotic checkpoint protein, though by a different mechanism. While BubR1 suppression abolished spindle checkpoint functions, which is a requirement for cell death after release from the spindle checkpoint, SIRT2 downregulation prolonged chronic mitotic arrest from sustained activation of the mitotic checkpoint and consequently prevented a shift to secondary outcomes, including cell death, after release from chronic mitotic arrest. Consistent with this notion, BubR1 downregulation was dominant over SIRT2 knockdown in regard to mitotic regulation in the presence of nocodazole. These results suggest that SIRT2 functions to release chronic mitotic arrest in cells treated with MTIs, leading to other outcomes. We also found that SIRT2 downregulation caused centrosome fragmentation in response to nocodazole prior to the alteration in spindle checkpoint function, implying not only a novel function of SIRT2 for centrosome maintenance upon exposure to mitotic stress caused by MTIs, but also the existence of a centrosome-mediated signaling pathway to sustain the spindle checkpoint. Therefore, this study highlights a novel pathway leading to resistance to MTIs, in which SIRT2 downregulation participates.
authors.affiliation: Division of Human Genome Science, Department of Molecular and Cellular Biology, School of Life Sciences, Faculty of Medicine, Tottori University, Yonago, Tottori, Japan. toshiaki.inoue.nishida@gmail.com
authors.forename: Toshiaki
authors.initials: T
authors.lastname: Inoue
authors.forename: Yuji
authors.initials: Y
authors.lastname: Nakayama
authors.forename: Hidetoshi
authors.initials: H
authors.lastname: Yamada
authors.forename: Yanze C
authors.initials: YC
authors.lastname: Li
authors.forename: Shigeyuki
authors.initials: S
authors.lastname: Yamaguchi
authors.forename: Mitsuhiko
authors.initials: M
authors.lastname: Osaki
authors.forename: Akihiro
authors.initials: A
authors.lastname: Kurimasa
authors.forename: Masaharu
authors.initials: M
authors.lastname: Hiratsuka
authors.forename: Motonobu
authors.initials: M
authors.lastname: Katoh
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Oshimura
mesh_terms: D018385:Centrosome / Q000187:drug effects / Q000378:metabolism; D015536:Down-Regulation / Q000187:drug effects*; D019008:Drug Resistance, Neoplasm / Q000187:drug effects*; D045325:HCT116 Cells; D006801:Humans; D008870:Microtubules / Q000187:drug effects* / Q000378:metabolism; D008938:Mitosis / Q000187:drug effects*; D015739:Nocodazole / Q000494:pharmacology; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism; D056565:Sirtuin 2; D037761:Sirtuins / Q000378:metabolism*; D050257:Tubulin Modulators / Q000494:pharmacology*
chemical_list: D034741:RNA, Small Interfering; D050257:Tubulin Modulators; C584277:BUB1 protein, human; C090464:Bub1 spindle checkpoint protein; D017346:Protein Serine-Threonine Kinases; C474199:SIRT2 protein, human; D056565:Sirtuin 2; D037761:Sirtuins; D015739:Nocodazole