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Expression of E. coli RecA targeted to mitochondria of human cells
R Paul1, R Dalibart, S Lemoine
1EMI 99.29 INSERM, Génétique Mitochondriale, Université Victor Segalen Bordeaux 2, 146 rue Léo Saignat, 33076 Cedex, Bordeaux, France.
Abstract:
Mitochondrial DNA integrity is ensured by several nuclear-encoded proteins in vertebrates, and a number of mtDNA alterations in human diseases, including deletions and duplications, have been suspected to result from errors in the mitochondrial recombination pathway. However, the presence of the latter system is still a matter of controversy as RecA proteins display various functions in vitro. In Escherichia coli, RecA plays a central role in homologous recombination by pairing and transferring a single strand to a homologous duplex DNA. To address indirectly the issue of a mitochondrial recombination pathway in vivo, we have constructed a chimeric gene containing an N terminal mitochondrial targeting sequence and the E. coli RecA gene. Cells were transfected by the recombinant plasmid, then tested for their mtDNA repair upon bleomycin treatment. We found an increased repair rate of the mitochondrial DNA in cells expressing RecA as compared to control cells. These results indicate that the transfected cells display an improved mtDNA repair replication pathway due to the exogenous RecA, likely in synergy with an endogenous rate-limiting mitochondrial recombination pathway.
Insights
This study investigated mitochondrial DNA repair mechanisms. Expressing E. coli RecA protein in cells enhanced mitochondrial DNA repair, suggesting a role for recombination pathways in maintaining DNA integrity.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Mitochondrial DNA (mtDNA) integrity is crucial for cellular function and is maintained by nuclear-encoded proteins.
- mtDNA alterations like deletions and duplications are linked to human diseases.
- The existence and function of a mitochondrial recombination pathway remain debated, partly due to the diverse in vitro functions of RecA proteins.
Purpose of the Study:
- To indirectly investigate the presence and function of a mitochondrial recombination pathway in vivo.
- To determine if bacterial RecA protein can enhance mitochondrial DNA repair in eukaryotic cells.
Main Methods:
- A chimeric gene was constructed, fusing a mitochondrial targeting sequence with the E. coli RecA gene.
- Human cells were transfected with the recombinant plasmid.
- The ability of transfected cells to repair mtDNA after bleomycin treatment was assessed.
Main Results:
- Cells expressing the chimeric RecA gene showed a significantly increased rate of mitochondrial DNA repair compared to control cells.
- This suggests that exogenous RecA protein can bolster mtDNA repair processes.
Conclusions:
- The findings support the hypothesis of an endogenous, potentially rate-limiting, mitochondrial recombination pathway.
- Exogenous RecA expression can enhance mitochondrial DNA repair replication, likely by interacting with or complementing endogenous pathways.