Microhomology-mediated end joining is the principal mediator of double-strand break repair during mitochondrial DNA lesions
| Autor: | Ravi K. Babu, Satish Kumar Tadi, Robin Sebastian, Sathees C. Raghavan, Sumedha Dahal, Bibha Choudhary |
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| Rok vydání: | 2016 |
| Předmět: |
0301 basic medicine
Mitochondrial DNA DNA End-Joining Repair Mitochondrial disease Biology Mitochondrion DNA Mitochondrial Biochemistry DNA Ligase ATP 03 medical and health sciences 0302 clinical medicine PARP1 medicine Animals Humans DNA Breaks Double-Stranded Molecular Biology Genetics chemistry.chemical_classification DNA ligase Recombinational DNA Repair Articles Cell Biology medicine.disease Mitochondria Rats Nuclear DNA Cell biology DNA-Binding Proteins enzymes and coenzymes (carbohydrates) 030104 developmental biology Microhomology-mediated end joining chemistry Cell Biology of Disease 030220 oncology & carcinogenesis HeLa Cells |
| Zdroj: | Molecular Biology of the Cell |
| ISSN: | 2381-3652 |
| Popis: | Repair of double-strand breaks in mammalian mitochondria depends on microhomology-mediated end joining (MMEJ). Classical NHEJ is not detectable in mitochondria. DNA ligase III, but not ligase IV or ligase I, is involved in mitochondrial MMEJ. The protein machinery involved in miitochondrial MMEJ includes CtIP, FEN1, ligase III, MRE11, and PARP1. Mitochondrial DNA (mtDNA) deletions are associated with various mitochondrial disorders. The deletions identified in humans are flanked by short, directly repeated mitochondrial DNA sequences; however, the mechanism of such DNA rearrangements has yet to be elucidated. In contrast to nuclear DNA (nDNA), mtDNA is more exposed to oxidative damage, which may result in double-strand breaks (DSBs). Although DSB repair in nDNA is well studied, repair mechanisms in mitochondria are not characterized. In the present study, we investigate the mechanisms of DSB repair in mitochondria using in vitro and ex vivo assays. Whereas classical NHEJ (C-NHEJ) is undetectable, microhomology-mediated alternative NHEJ efficiently repairs DSBs in mitochondria. Of interest, robust microhomology-mediated end joining (MMEJ) was observed with DNA substrates bearing 5-, 8-, 10-, 13-, 16-, 19-, and 22-nt microhomology. Furthermore, MMEJ efficiency was enhanced with an increase in the length of homology. Western blotting, immunoprecipitation, and protein inhibition assays suggest the involvement of CtIP, FEN1, MRE11, and PARP1 in mitochondrial MMEJ. Knockdown studies, in conjunction with other experiments, demonstrated that DNA ligase III, but not ligase IV or ligase I, is primarily responsible for the final sealing of DSBs during mitochondrial MMEJ. These observations highlight the central role of MMEJ in maintenance of mammalian mitochondrial genome integrity and is likely relevant for deletions observed in many human mitochondrial disorders. |
| Databáze: | OpenAIRE |
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