Recombination-dependent mtDNA partitioning: in vivo role of Mhr1p to promote pairing of homologous DNA

EMBO J. 2002 Sep 2;21(17):4730-40. doi: 10.1093/emboj/cdf466.


Yeast mhr1-1 was isolated as a defective mutation in mitochondrial DNA (mtDNA) recombination. About half of mhr1-1 cells lose mtDNA during growth at a higher temperature. Here, we show that mhr1-1 exhibits a defect in the partitioning of nascent mtDNA into buds and is a base-substitution mutation in MHR1 encoding a mitochondrial matrix protein. We found that the Mhr1 protein (Mhr1p) has activity to pair single-stranded DNA and homologous double-stranded DNA to form heteroduplex joints in vitro, and that mhr1-1 causes the loss of this activity, indicating its role in homologous mtDNA recombination. While the majority of the mtDNA in the mother cells consists of head-to-tail concatemers, more than half of the mtDNA in the buds exists as genome-sized monomers. The mhr1-1 deltacce1 double mutant cells do not maintain any mtDNA, indicating the strict dependence of mtDNA maintenance on recombination functions. These results suggest a mechanism for mtDNA inheritance similar to that operating in the replication and packaging of phage DNA.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Substitution
  • DNA / genetics
  • DNA / metabolism
  • DNA, Circular / genetics
  • DNA, Circular / metabolism
  • DNA, Fungal / genetics
  • DNA, Fungal / metabolism*
  • DNA, Mitochondrial / genetics
  • DNA, Mitochondrial / metabolism*
  • DNA, Single-Stranded / genetics
  • DNA, Single-Stranded / metabolism
  • Extrachromosomal Inheritance / genetics*
  • Models, Genetic
  • Mutation, Missense
  • Nuclear Proteins / genetics
  • Nuclear Proteins / physiology*
  • Point Mutation
  • Recombination, Genetic / genetics*
  • Reproduction, Asexual
  • Saccharomyces cerevisiae / genetics*
  • Saccharomyces cerevisiae / growth & development
  • Saccharomyces cerevisiae Proteins / genetics
  • Saccharomyces cerevisiae Proteins / physiology*
  • Sequence Homology, Nucleic Acid
  • Transcription Factors*


  • DNA, Circular
  • DNA, Fungal
  • DNA, Mitochondrial
  • DNA, Single-Stranded
  • MHR1 protein, S cerevisiae
  • Nuclear Proteins
  • Saccharomyces cerevisiae Proteins
  • Transcription Factors
  • DNA