title: ATM mediates oxidative stress-induced dephosphorylation of DNA ligase IIIalpha.
abstract: Among the three mammalian genes encoding DNA ligases, only the LIG3 gene does not have a homolog in lower eukaryotes. In somatic mammalian cells, the nuclear form of DNA ligase IIIalpha forms a stable complex with the DNA repair protein XRCC1 that is also found only in higher eukaryotes. Recent studies have shown that XRCC1 participates in S phase-specific DNA repair pathways independently of DNA ligase IIIalpha and is constitutively phosphorylated by casein kinase II. In this study we demonstrate that DNA ligase IIIalpha, unlike XRCC1, is phosphorylated in a cell cycle-dependent manner. Specifically, DNA ligase IIIalpha is phosphorylated on Ser123 by the cell division cycle kinase Cdk2 beginning early in S phase and continuing into M phase. Interestingly, treatment of S phase cells with agents that cause oxygen free radicals induces the dephosphorylation of DNA ligase IIIalpha. This oxidative stress-induced dephosphorylation of DNA ligase IIIalpha is dependent upon the ATM (ataxia-telangiectasia mutated) kinase and appears to involve inhibition of Cdk2 and probably activation of a phosphatase.
authors.affiliation: Molecular and Cell Biology Graduate Program Baltimore, MD 21201-1509, USA.
authors.forename: Zhiwan
authors.initials: Z
authors.lastname: Dong
authors.forename: Alan E
authors.initials: AE
authors.lastname: Tomkinson
mesh_terms: D064007:Ataxia Telangiectasia Mutated Proteins; D018797:Cell Cycle Proteins / Q000378:metabolism*; D045744:Cell Line, Tumor; D051357:Cyclin-Dependent Kinase 2 / Q000378:metabolism; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000378:metabolism*; D006801:Humans; D018384:Oxidative Stress; D010766:Phosphorylation; D000075223:Poly-ADP-Ribose Binding Proteins; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism*; D016196:S Phase; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D029867:Xenopus Proteins
chemical_list: D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D000075223:Poly-ADP-Ribose Binding Proteins; D025521:Tumor Suppressor Proteins; D029867:Xenopus Proteins; C576324:ATM protein, human; D064007:Ataxia Telangiectasia Mutated Proteins; D017346:Protein Serine-Threonine Kinases; D051357:Cyclin-Dependent Kinase 2; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618817:LIG3 protein, human