title: Rapid degradation of Cdt1 upon UV-induced DNA damage is mediated by SCFSkp2 complex.
abstract: Cdt1 is a licensing factor for DNA replication, the function of which is tightly controlled to maintain genome integrity. Previous studies have indicated that the cell cycle-dependent degradation of Cdt1 is triggered at S phase to prevent re-replication. In this study, we found that Cdt1 is degraded upon DNA damage induced by either UV treatment or gamma-irradiation (IR). Although the IR-triggered degradation of Cdt1 was caffeine-insensitive, the UV-triggered degradation of Cdt1 was caffeine-sensitive. This indicates that the cells treated with UV utilize the checkpoint pathway, which differs from that triggered by IR. A recent study has suggested that Cdt1 is phosphorylated, ubiquitylated, and degraded at the G(1)/S boundary in the normal cell cycle. Treatment with MG132, a proteasome inhibitor, inhibited the degradation of Cdt1 and resulted in the accumulation of the phosphorylated form of Cdt1 after UV treatment. In the case of UV treatment, phosphorylation of Cdt1 induced the recruitment of Cdt1 to a SCF(Skp2) complex. Moreover, ectopic overexpression of Cdt1 after UV treatment interfered the inhibition of DNA synthesis. These results indicate that Cdt1 is a target molecule of the cell cycle checkpoint in UV-induced DNA damage.
authors.affiliation: Department of Gastroenterology and Hematology, Hokkaido University Graduate School of Medicine, Kita 15, Nishi 7, Kita-ku, Sapporo, Hokkaido 060-8638, Japan. t-kondoh@med.hokudai.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Kondo
authors.forename: Masanobu
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Junko
authors.initials: J
authors.lastname: Tanaka
authors.forename: Akiko
authors.initials: A
authors.lastname: Yokoyama
authors.forename: Sachiko
authors.initials: S
authors.lastname: Suzuki
authors.forename: Naoko
authors.initials: N
authors.lastname: Kato
authors.forename: Masahiro
authors.initials: M
authors.lastname: Onozawa
authors.forename: Kohji
authors.initials: K
authors.lastname: Chiba
authors.forename: Satoshi
authors.initials: S
authors.lastname: Hashino
authors.forename: Masahiro
authors.initials: M
authors.lastname: Imamura
authors.forename: Yasuhiro
authors.initials: Y
authors.lastname: Minami
authors.forename: Naoto
authors.initials: N
authors.lastname: Minamino
authors.forename: Masahiro
authors.initials: M
authors.lastname: Asaka
mesh_terms: D002110:Caffeine / Q000494:pharmacology; D002453:Cell Cycle / Q000502:physiology; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D045744:Cell Line, Tumor; D004249:DNA Damage / Q000502:physiology*; D004261:DNA Replication / Q000502:physiology; D004791:Enzyme Inhibitors / Q000494:pharmacology; D006367:HeLa Cells; D006801:Humans; D007259:Infrared Rays; D007976:Leupeptins / Q000494:pharmacology; D010766:Phosphorylation; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D044786:S-Phase Kinase-Associated Proteins / Q000235:genetics / Q000378:metabolism*; D019311:Staurosporine / Q000031:analogs & derivatives* / Q000494:pharmacology; D025801:Ubiquitin / Q000378:metabolism; D014466:Ultraviolet Rays
chemical_list: C467199:CDT1 protein, human; D018797:Cell Cycle Proteins; D004791:Enzyme Inhibitors; D007976:Leupeptins; D011994:Recombinant Proteins; D044786:S-Phase Kinase-Associated Proteins; D025801:Ubiquitin; D002110:Caffeine; C054852:7-hydroxystaurosporine; D019311:Staurosporine; C072553:benzyloxycarbonylleucyl-leucyl-leucine aldehyde