A role for MHR1, a gene required for mitochondrial genetic recombination, in the repair of damage spontaneously introduced in yeast mtDNA.
A nuclear recessive mutant in Saccharomyces cerevisiae, mhr1-1, is defective in mitochondrial genetic recombination at 30 degrees C and shows extensive vegetative petite induction by UV irradiation at 30 degrees C or when cultivated at a higher temperature (37 degrees C). It has been postulated that mitochondrial DNA (mtDNA) is oxidatively damaged by by-products of oxidative respiration. Since genetic recombination plays a critical role in DNA repair in various organisms, we tested the possibility that MHR1 plays a role in the repair of oxidatively damaged mtDNA using an enzyme assay. mtDNA isolated from cells grown under standard (aerobic) conditions contained a much higher level of DNA lesions compared with mtDNA isolated from anaerobically grown cells. Soon after a temperature shift from 30 to 37 degrees C the number of mtDNA lesions increased 2-fold in mhr1-1 mutant cells but not in MHR1 cells. Malonic acid, which decreased the oxidative stress in mitochondria, partially suppressed both petite induction and the temperature-induced increase in the amount of mtDNA damage in mhr1-1 cells at 37 degrees C. Thus, functional mitochondria require active MHR1, which keeps the extent of spontaneous oxidative damage in mtDNA within a tolerable level. These observations are consistent with MHR1 having a possible role in mtDNA repair.
Ling
F
F
Cellular and Molecular Biology Laboratory, RIKEN (The Institute of Physical and Chemical Research), Hirosawa 2-1, Wako-shi, Saitama 351-01, Japan.
Morioka
H
H
Ohtsuka
E
E
Shibata
T
T
D000332:Aerobiosis; D000496:Alloxan / Q000494:pharmacology; D002952:Citric Acid Cycle / Q000187:drug effects; D004249:DNA Damage / Q000235:genetics* / Q000528:radiation effects; D004260:DNA Repair / Q000187:drug effects / Q000235:genetics*; D004271:DNA, Fungal / Q000235:genetics / Q000378:metabolism; D004272:DNA, Mitochondrial / Q000235:genetics*; D003576:Electron Transport Complex IV / Q000037:antagonists & inhibitors / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism*; D005800:Genes, Fungal / Q000235:genetics; D008314:Malonates / Q000494:pharmacology; D008928:Mitochondria / Q000187:drug effects / Q000235:genetics / Q000378:metabolism / Q000528:radiation effects; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics / Q000528:radiation effects; D009687:Nuclear Proteins / Q000378:metabolism*; D016877:Oxidants / Q000494:pharmacology; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D011995:Recombination, Genetic / Q000235:genetics*; D015203:Reproducibility of Results; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism / Q000528:radiation effects; D029701:Saccharomyces cerevisiae Proteins; D019810:Sodium Azide / Q000494:pharmacology; D013696:Temperature; D014157:Transcription Factors; D014466:Ultraviolet Rays
D004271:DNA, Fungal; D004272:DNA, Mitochondrial; D005656:Fungal Proteins; C417727:MHR1 protein, S cerevisiae; D008314:Malonates; D009687:Nuclear Proteins; D016877:Oxidants; D017382:Reactive Oxygen Species; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000496:Alloxan; D019810:Sodium Azide; C030290:malonic acid; D003576:Electron Transport Complex IV