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Updated: May 13, 2025
Genotyping Single Nucleotide Polymorphisms in the Mitochondrial Genome by Pyrosequencing
Published on: February 10, 2023
The POLγ Y951N patient mutation disrupts the switch between DNA synthesis and proofreading, triggering mitochondrial
Josefin M E Forslund1, Tran V H Nguyen1, Vimal Parkash1
1Department of Medical Biochemistry and Biophysics, Umeå University, Umeå 90187, Sweden.
Abstract:
Mitochondrial DNA (mtDNA) stability, essential for cellular energy production, relies on DNA polymerase gamma (POLγ). Here, we show that the POLγ Y951N disease-causing mutation induces replication stalling and severe mtDNA depletion. However, unlike other POLγ disease-causing mutations, Y951N does not directly impair exonuclease activity and only mildly affects polymerase activity. Instead, we found that Y951N compromises the enzyme's ability to efficiently toggle between DNA synthesis and degradation, and is thus a patient-derived mutation with impaired polymerase-exonuclease switching. These findings provide insights into the intramolecular switch when POLγ proofreads the newly synthesized DNA strand and reveal a new mechanism for causing mitochondrial DNA instability.
Insights
A DNA polymerase gamma (POLγ) mutation causes mitochondrial DNA depletion by impairing its switching between synthesis and degradation. This study reveals a new mechanism for mitochondrial DNA instability.
Area of Science:
- Molecular Biology
- Genetics
- Biochemistry
Background:
- Mitochondrial DNA (mtDNA) stability is crucial for cellular energy production.
- DNA polymerase gamma (POLγ) is essential for maintaining mtDNA integrity.
- Mutations in POLγ can lead to severe mitochondrial disorders.
Purpose of the Study:
- To investigate the mechanism by which the POLγ Y951N mutation causes mtDNA instability.
- To understand the role of polymerase-exonuclease switching in POLγ function.
Main Methods:
- Analysis of the POLγ Y951N mutation's effect on polymerase and exonuclease activity.
- Assessment of replication stalling and mtDNA depletion in cells with the Y951N mutation.
Main Results:
- The Y951N mutation causes replication stalling and severe mtDNA depletion.
- Unlike other disease-causing mutations, Y951N does not significantly impair polymerase or exonuclease activity directly.
- Y951N compromises the enzyme's ability to switch between DNA synthesis and degradation.
Conclusions:
- The POLγ Y951N mutation impairs polymerase-exonuclease switching, leading to mtDNA instability.
- This study identifies a novel mechanism contributing to mitochondrial DNA depletion disorders.
- Findings offer insights into POLγ's proofreading mechanism and intramolecular switching.
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