DNA recombination-initiation plays a role in the extremely biased inheritance of yeast [rho-] mitochondrial DNA that contains the replication origin ori5.
Hypersuppressiveness, as observed in Saccharomyces cerevisiae, is an extremely biased inheritance of a small mitochondrial DNA (mtDNA) fragment that contains a replication origin (HS [rho(-)] mtDNA). Our previous studies showed that concatemers (linear head-to-tail multimers) are obligatory intermediates for mtDNA partitioning and are primarily formed by rolling-circle replication mediated by Mhr1, a protein required for homologous mtDNA recombination. In this study, we found that Mhr1 is required for the hypersuppressiveness of HS [ori5] [rho(-)] mtDNA harboring ori5, one of the replication origins of normal ([rho(+)]) mtDNA. In addition, we detected an Ntg1-stimulated double-strand break at the ori5 locus. Purified Ntg1, a base excision repair enzyme, introduced a double-stranded break by itself into HS [ori5] [rho(-)] mtDNA at ori5 isolated from yeast cells. Both hypersuppressiveness and concatemer formation of HS [ori5] [rho(-)] mtDNA are simultaneously suppressed by the ntg1 null mutation. These results support a model in which, like homologous recombination, rolling-circle HS [ori5] [rho(-)] mtDNA replication is initiated by double-stranded breakage in ori5, followed by Mhr1-mediated homologous pairing of the processed nascent DNA ends with circular mtDNA. The hypersuppressiveness of HS [ori5] [rho(-)] mtDNA depends on a replication advantage furnished by the higher density of ori5 sequences and on a segregation advantage furnished by the higher genome copy number on transmitted concatemers.
Ling
Feng
F
RIKEN Discovery Research Institute, Hirosawa 2-1, Wako-shi, Saitama 351-0198, Japan.
Hori
Akiko
A
Shibata
Takehiko
T
D000496:Alloxan / Q000494:pharmacology; D053903:DNA Breaks, Double-Stranded / Q000187:drug effects; D044708:DNA, Concatenated / Q000378:metabolism; D004271:DNA, Fungal / Q000378:metabolism*; D004272:DNA, Mitochondrial / Q000235:genetics* / Q000378:metabolism*; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; D005111:Extrachromosomal Inheritance / Q000235:genetics*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D009699:N-Glycosyl Hydrolases / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism; D018384:Oxidative Stress / Q000187:drug effects; D011995:Recombination, Genetic / Q000187:drug effects; D018741:Replication Origin / Q000187:drug effects / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics*; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D013489:Suppression, Genetic / Q000187:drug effects; D014157:Transcription Factors / Q000378:metabolism
D044708:DNA, Concatenated; D004271:DNA, Fungal; D004272:DNA, Mitochondrial; C417727:MHR1 protein, S cerevisiae; D009687:Nuclear Proteins; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000496:Alloxan; D009699:N-Glycosyl Hydrolases; D043603:DNA-(Apurinic or Apyrimidinic Site) Lyase; C101825:NTG1 protein, S cerevisiae