Short, single-stranded oligonucleotides mediate targeted nucleotide conversion using extracts from isolated liver...

Area of Science:

• Mitochondrial Biology
• Molecular Genetics
• DNA Repair Mechanisms

Background:

• Human diseases often stem from single-point mutations in mitochondrial DNA.
• Previous work showed rat liver mitochondria can modify DNA using chimeric oligonucleotides (ONs).
• Nuclear and mitochondrial DNA repair pathways involve different factors and mechanisms.

Purpose of the Study:

• To investigate if mitochondria have the enzymatic machinery for single-stranded (SS) oligonucleotide-mediated DNA alterations.
• To determine if SS ONs can correct point mutations in mitochondrial DNA.

Main Methods:

• In vitro DNA repair assays using mutagenized plasmids.
• A bacterial read-out system to detect nucleotide modifications.
• Protein extracts from purified rat liver mitochondria and nuclei were utilized.

Main Results:

• Mitochondrial and nuclear extracts showed similar levels of site-specific nucleotide modifications with SS ONs.
• Quiescent liver extracts yielded higher conversion rates than regenerating liver extracts.
• SS ON-mediated correction appears to be a single-strand, strand-transfer process.

Conclusions:

• Mitochondria possess factors necessary for correcting single-point mutations using SS ONs.
• These factors differ from those required for chimeric ON-mediated DNA repair.
• Unmodified SS ONs may offer a novel therapeutic strategy for mitochondrial diseases.