title: Regulation and functional contribution of thymidine kinase 1 in repair of DNA damage.
abstract: Cellular supply of dNTPs is essential in the DNA replication and repair processes. Here we investigated the regulation of thymidine kinase 1 (TK1) in response to DNA damage and found that genotoxic insults in tumor cells cause up-regulation and nuclear localization of TK1. During recovery from DNA damage, TK1 accumulates in p53-null cells due to a lack of mitotic proteolysis as these cells are arrested in the G(2) phase by checkpoint activation. We show that in p53-proficient cells, p21 expression in response to DNA damage prohibits G(1)/S progression, resulting in a smaller G(2) fraction and less TK1 accumulation. Thus, the p53 status of tumor cells affects the level of TK1 after DNA damage through differential cell cycle control. Furthermore, it was shown that in HCT-116 p53(-/-) cells, TK1 is dispensable for cell proliferation but crucial for dTTP supply during recovery from DNA damage, leading to better survival. Depletion of TK1 decreases the efficiency of DNA repair during recovery from DNA damage and generates more cell death. Altogether, our data suggest that more dTTP synthesis via TK1 take place after genotoxic insults in tumor cells, improving DNA repair during G(2) arrest.
authors.affiliation: Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan.
authors.forename: Yen-Ling
authors.initials: YL
authors.lastname: Chen
authors.affiliation: Department of Anatomy, Physiology and Biochemistry, The Swedish University of Agricultural Sciences, Biomedical Center, S-751 23 Uppsala, Sweden.
authors.forename: Staffan
authors.initials: S
authors.lastname: Eriksson
authors.affiliation: Graduate Institute of Biochemistry and Molecular Biology, College of Medicine, National Taiwan University, No. 1, Section 1, Jen-Ai Road, Taipei 100, Taiwan; Institute of Biochemistry and Molecular Biology, National Yang-Ming University, No. 155, Section 2, Linong Street, Taipei 112, Taiwan. Electronic address: ZFCHANG@ym.edu.tw.
authors.forename: Zee-Fen
authors.initials: ZF
authors.lastname: Chang
mesh_terms: D045744:Cell Line, Tumor; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000235:genetics / Q000378:metabolism; D004249:DNA Damage; D004260:DNA Repair / Q000235:genetics; D004261:DNA Replication / Q000235:genetics; D006801:Humans; D007399:Interphase; D009369:Neoplasms / Q000201:enzymology* / Q000235:genetics; D013937:Thymidine Kinase / Q000235:genetics / Q000378:metabolism*; D013942:Thymine Nucleotides / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000235:genetics / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; C495901:TP53 protein, human; D013942:Thymine Nucleotides; D016159:Tumor Suppressor Protein p53; D013937:Thymidine Kinase; C092717:thymidine kinase 1; C024157:thymidine 5'-triphosphate