title: Mitochondrial DNA ligase is dispensable for the viability of cultured cells but essential for mtDNA maintenance.
abstract: Multiple lines of evidence support the notion that DNA ligase III (LIG3), the only DNA ligase found in mitochondria, is essential for viability in both whole organisms and in cultured cells. Previous attempts to generate cells devoid of mitochondrial DNA ligase failed. Here, we report, for the first time, the derivation of viable LIG3-deficient mouse embryonic fibroblasts. These cells lack mtDNA and are auxotrophic for uridine and pyruvate, which may explain the apparent lethality of the Lig3 knock-out observed in cultured cells in previous studies. Cells with severely reduced expression of LIG3 maintain normal mtDNA copy number and respiration but show reduced viability in the face of alkylating and oxidative damage, increased mtDNA degradation in response to oxidative damage, and slow recovery from mtDNA depletion. Our findings clarify the cellular role of LIG3 and establish that the loss of viability in LIG3-deficient cells is conditional and secondary to the ρ(0) phenotype.
authors.affiliation: From the Departments of Cell Biology and Neuroscience and.
authors.forename: Inna N
authors.initials: IN
authors.lastname: Shokolenko
authors.forename: Rafik Z
authors.initials: RZ
authors.lastname: Fayzulin
authors.forename: Sachin
authors.initials: S
authors.lastname: Katyal
authors.forename: Peter J
authors.initials: PJ
authors.lastname: McKinnon
authors.forename: Glenn L
authors.initials: GL
authors.lastname: Wilson
authors.forename: Mikhail F
authors.initials: MF
authors.lastname: Alexeyev
mesh_terms: D000483:Alleles; D000818:Animals; D003433:Crosses, Genetic; D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000235:genetics / Q000378:metabolism*; D004260:DNA Repair; D004272:DNA, Mitochondrial / Q000235:genetics*; D005347:Fibroblasts / Q000378:metabolism; D005838:Genotype; D006367:HeLa Cells; D006801:Humans; D051379:Mice; D018613:Microscopy, Confocal; D008928:Mitochondria / Q000201:enzymology*; D024101:Mitochondrial Proteins / Q000235:genetics / Q000378:metabolism*; D009841:Oligonucleotides / Q000235:genetics; D018384:Oxidative Stress; D010641:Phenotype; D000075223:Poly-ADP-Ribose Binding Proteins; D029867:Xenopus Proteins
chemical_list: D004272:DNA, Mitochondrial; D024101:Mitochondrial Proteins; D009841:Oligonucleotides; D000075223:Poly-ADP-Ribose Binding Proteins; D029867:Xenopus Proteins; D011088:DNA Ligases; D000072481:DNA Ligase ATP; C000618816:DNA ligase III alpha protein, Xenopus; C000618817:LIG3 protein, human; C000618818:Lig3 protein, mouse
keywords: DNA Damage; DNA Repair; DNA Replication; Mitochondria; Mitochondrial DNA; Mitochondrial DNA Degradation; Reactive Oxygen Species; Respiration; rho-0 Cells