Prevention of mitochondrial genomic instability in yeast by the mitochondrial recombinase Mhr1

Sci Rep. 2019 Apr 1;9(1):5433. doi: 10.1038/s41598-019-41699-9.

Abstract

Mitochondrial (mt) DNA encodes factors essential for cellular respiration, therefore its level and integrity are crucial. ABF2 encodes a mitochondrial DNA-binding protein and its null mutation (Δabf2) induces mtDNA instability in Saccharomyces cerevisiae. Mhr1 is a mitochondrial recombinase that mediates the predominant form of mtDNA replication and acts in mtDNA segregation and the repair of mtDNA double-stranded breaks (DSBs). However, the involvement of Mhr1 in prevention of mtDNA deletion mutagenesis is unknown. In this study we used Δabf2 mhr1-1 double-mutant cells, which lose mitochondrial function in media containing fermentable carbon sources, to investigate whether Mhr1 is a suppressor of mtDNA deletion mutagenesis. We used a suppresivity assay and Southern blot analysis to reveal that the Δabf2 mutation causes mtDNA deletions rather than an mtDNA-lacking (ρ0) phenotype, and observed that mtDNA deletions are exacerbated by an additional mhr1-1 mutation. Loss of respiratory function due to mtDNA fragmentation occurred in ∆mhr1 and ∆abf2 mhr1-1 cells. However, exogenous introduction of Mhr1 into Δabf2 mhr1-1 cells significantly rescued respiratory growth, suggesting that Mhr1-driven homologous mtDNA recombination prevents mtDNA instability.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Culture Media
  • Fermentation
  • Genome, Mitochondrial*
  • Genomic Instability*
  • Mutation
  • Point Mutation
  • Recombination, Genetic
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*

Substances

  • Culture Media
  • MHR1 protein, S cerevisiae
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors