Recombination-dependent mtDNA partitioning: in vivo role of Mhr1p to promote pairing of homologous DNA.
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.
Cellular & Molecular Biology Laboratory, RIKEN, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan.
Feng
F
Ling
Takehiko
T
Shibata
D019943:Amino Acid Substitution; D004247:DNA / Q000235:genetics / Q000378:metabolism; D004270:DNA, Circular / Q000235:genetics / Q000378:metabolism; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism*; D004272:DNA, Mitochondrial / Q000235:genetics / Q000378:metabolism*; D004277:DNA, Single-Stranded / Q000235:genetics / Q000378:metabolism; D005111:Extrachromosomal Inheritance / Q000235:genetics*; D008957:Models, Genetic; D020125:Mutation, Missense; D009687:Nuclear Proteins / Q000235:genetics / Q000502:physiology*; D017354:Point Mutation; D011995:Recombination, Genetic / Q000235:genetics*; D012100:Reproduction, Asexual; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000254:growth & development; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000502:physiology*; D012689:Sequence Homology, Nucleic Acid; D014157:Transcription Factors
D004270:DNA, Circular; D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D004277:DNA, Single-Stranded; C417727:MHR1 protein, S cerevisiae; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D004247:DNA