title: Nuclear export of cyclin B1 and its possible role in the DNA damage-induced G2 checkpoint.
abstract: M-phase-promoting factor (MPF), a complex of cdc2 and a B-type cyclin, is a key regulator of the G2/M cell cycle transition. Cyclin B1 accumulates in the cytoplasm through S and G2 phases and translocates to the nucleus during prophase. We show here that cytoplasmic localization of cyclin B1 during interphase is directed by its nuclear export signal (NES)-dependent transport mechanism. Treatment of HeLa cells with leptomycin B (LMB), a specific inhibitor of the NES-dependent transport, resulted in nuclear accumulation of cyclin B1 in G2 phase. Disruption of an NES which has been identified in cyclin B1 here abolished the nuclear export of this protein, and consequently the NES-disrupted cyclin B1 when expressed in cells accumulated in the nucleus. Moreover, we show that expression of the NES-disrupted cyclin B1 or LMB treatment of the cells is able to override the DNA damage-induced G2 checkpoint when combined with caffeine treatment. These results suggest a role of nuclear exclusion of cyclin B1 in the DNA damage-induced G2 checkpoint.
authors.affiliation: Department of Biophysics, Graduate School of Science, Kyoto University, Kyoto, Japan.
authors.forename: F
authors.initials: F
authors.lastname: Toyoshima
authors.forename: T
authors.initials: T
authors.lastname: Moriguchi
authors.forename: A
authors.initials: A
authors.lastname: Wada
authors.forename: M
authors.initials: M
authors.lastname: Fukuda
authors.forename: E
authors.initials: E
authors.lastname: Nishida
mesh_terms: D000818:Animals; D001665:Binding Sites; D001692:Biological Transport; D002110:Caffeine / Q000494:pharmacology; D002352:Carrier Proteins / Q000037:antagonists & inhibitors; D002467:Cell Nucleus / Q000378:metabolism; D019926:Cyclin B / Q000378:metabolism*; D056744:Cyclin B1; D003593:Cytoplasm / Q000378:metabolism; D004249:DNA Damage; D005047:Etoposide / Q000494:pharmacology; D005231:Fatty Acids, Unsaturated / Q000494:pharmacology; D016195:G2 Phase; D006367:HeLa Cells; D006801:Humans; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D000097606:Exportin 1 Protein
chemical_list: D002110:Caffeine; D002352:Carrier Proteins; D019926:Cyclin B; D056744:Cyclin B1; D005047:Etoposide; D005231:Fatty Acids, Unsaturated; D028884:Karyopherins; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D000097606:Exportin 1 Protein; C534699:CCNB1 protein, human; C038753:leptomycin B