Molecular and structural basis for replication initiation and strand separation by human mitochondrial DNA polymerase γ.

Human mitochondrial DNA polymerase γ initiates replication with high stability on RNA primers, enabling strand separation through a unique mechanism involving novel structural elements.

• Why it matters: Understanding the molecular details of mtDNA replication is crucial because defects can cause severe mitochondrial diseases, yet these early steps and their fidelity are poorly understood.
• What they did: The study used structural analysis and mutagenesis to examine Polγ's interactions with RNA-DNA primers, revealing its intrinsic strand-displacement activity and unique strand separation mechanism involving the catcher and GP loop.
• The result: Findings clarify how Polγ initiates replication and separates strands, providing insights into mitochondrial disease mechanisms and potential targets for therapeutic intervention.