Sequence-specific modification of mitochondrial DNA using a chimeric zinc finger methylase

Area of Science:

• Molecular Biology
• Genetics
• Biotechnology

Background:

• Mitochondrial DNA (mtDNA) harbors genes crucial for cellular energy production.
• Mutations in mtDNA are linked to various inherited diseases.
• Targeting mtDNA for therapeutic interventions remains challenging due to delivery and specificity issues.

Purpose of the Study:

• To develop a method for sequence-specific targeting and modification of human mtDNA.
• To overcome limitations of conventional mitochondrial targeting sequences for engineered proteins.
• To demonstrate the potential for correcting disease-causing mtDNA mutations.

Main Methods:

• Engineered zinc finger peptides (ZFPs) were designed for selective binding to specific mtDNA sequences.
• A nuclear export signal was incorporated to facilitate ZFP import into mitochondria.
• ZFPs were combined with the hDNMT3a methylase activity to create a chimeric methylase for site-specific DNA alteration.
• The T8993G mutation, associated with NARP and Leigh's syndrome, was used as a target example.

Main Results:

• Engineered ZFPs required a nuclear export signal for efficient mitochondrial import, contrary to conventional targeting sequences.
• The chimeric methylase selectively methylated cytosines adjacent to the targeted T8993G mutation site in mtDNA.
• This demonstrated the feasibility of sequence-specific targeting and modification of human mtDNA.

Conclusions:

• Zinc finger technology, combined with a nuclear export signal and methylase activity, provides a viable strategy for sequence-specific mtDNA targeting and modification.
• This approach offers a proof of principle for developing novel therapeutic strategies for mitochondrial DNA diseases.