title: Glycogen Synthase Kinase 3 (GSK-3)-mediated Phosphorylation of Uracil N-Glycosylase 2 (UNG2) Facilitates the Repair of Floxuridine-induced DNA Lesions and Promotes Cell Survival.
abstract: Uracil N-glycosylase 2 (UNG2), the nuclear isoform of UNG, catalyzes the removal of uracil or 5-fluorouracil lesions that accumulate in DNA following treatment with the anticancer agents 5-fluorouracil and 5-fluorodeoxyuridine (floxuridine), a 5-fluorouracil metabolite. By repairing these DNA lesions before they can cause cell death, UNG2 promotes cancer cell survival and is therefore critically involved in tumor resistance to these agents. However, the mechanisms by which UNG2 is regulated remain unclear. Several phosphorylation sites within the N-terminal regulatory domain of UNG2 have been identified, although the effects of these modifications on UNG2 function have not been fully explored, nor have the identities of the kinases involved been determined. Here we show that glycogen synthase kinase 3 (GSK-3) interacts with and phosphorylates UNG2 at Thr60and that Thr60phosphorylation requires a Ser64priming phosphorylation event. We also show that mutating Thr60or Ser64to Ala increases the half-life of UNG2, reduces the rate of in vitro uracil excision, and slows UNG2 dissociation from chromatin after DNA replication. Using an UNG2-deficient ovarian cancer cell line that is hypersensitive to floxuridine, we show that GSK-3 phosphorylation facilitates UNG2-dependent repair of floxuridine-induced DNA lesions and promotes tumor cell survival following exposure to this agent. These data suggest that GSK-3 regulates UNG2 and promotes DNA damage repair.
authors.affiliation: From the Departments of Molecular Pharmacology and Experimental Therapeutics and.
authors.forename: Carly A
authors.initials: CA
authors.lastname: Baehr
authors.affiliation: From the Departments of Molecular Pharmacology and Experimental Therapeutics and.|the Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905-0002.
authors.forename: Catherine J
authors.initials: CJ
authors.lastname: Huntoon
authors.affiliation: From the Departments of Molecular Pharmacology and Experimental Therapeutics and.
authors.forename: Song-My
authors.initials: SM
authors.lastname: Hoang
authors.affiliation: From the Departments of Molecular Pharmacology and Experimental Therapeutics and.
authors.forename: Calvin R
authors.initials: CR
authors.lastname: Jerde
authors.affiliation: From the Departments of Molecular Pharmacology and Experimental Therapeutics and karnitz.larry@mayo.edu.|the Division of Oncology Research, Mayo Clinic, Rochester, Minnesota 55905-0002.|Radiation Oncology and.
authors.forename: Larry M
authors.initials: LM
authors.lastname: Karnitz
mesh_terms: D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism / Q000473:pathology; D002470:Cell Survival / Q000187:drug effects*; D045647:DNA Glycosylases / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair / Q000187:drug effects*; D004261:DNA Replication / Q000187:drug effects; D005260:Female; D005467:Floxuridine / Q000494:pharmacology; D005472:Fluorouracil / Q000494:pharmacology; D038362:Glycogen Synthase Kinase 3 / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D010051:Ovarian Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D010766:Phosphorylation; D014407:Tumor Cells, Cultured
chemical_list: D000964:Antimetabolites, Antineoplastic; D005467:Floxuridine; D038362:Glycogen Synthase Kinase 3; C492570:CCNO protein, human; D045647:DNA Glycosylases; D005472:Fluorouracil
keywords: DNA glycosylase; DNA repair; anticancer drug; base excision repair (BER); floxuridine; glycogen synthase kinase 3 (GSK-3); phosphorylation; serine/threonine protein kinase; uracil N-glycosylase 2 (UNG2)