The effects of mismatch repair and RAD1 genes on interchromosomal crossover recombination in Saccharomyces cerevisiae.
We have previously shown that recombination between 400-bp substrates containing only 4-bp differences, when present in an inverted repeat orientation, is suppressed by >20-fold in wild-type strains of S. cerevisiae. Among the genes involved in this suppression were three genes involved in mismatch repair--MSH2, MSH3, and MSH6--and one in nucleotide excision repair, RAD1. We now report the involvement of these genes in interchromosomal recombination occurring via crossovers using these same short substrates. In these experiments, recombination was stimulated by a double-strand break generated by the HO endonuclease and can occur between completely identical (homologous) substrates or between nonidentical (homeologous) substrates. In addition, a unique feature of this system is that recombining DNA strands can be given a choice of either type of substrate. We find that interchromosomal crossover recombination with these short substrates is severely inhibited in the absence of MSH2, MSH3, or RAD1 and is relatively insensitive to the presence of mismatches. We propose that crossover recombination with these short substrates requires the products of MSH2, MSH3, and RAD1 and that these proteins have functions in recombination in addition to the removal of terminal nonhomology. We further propose that the observed insensitivity to homeology is a result of the difference in recombinational mechanism and/or the timing of the observed recombination events. These results are in contrast with those obtained using longer substrates and may be particularly relevant to recombination events between the abundant short repeated sequences that characterize the genomes of higher eukaryotes.
Graduate Program in Genetics, and Molecular Biology, Emory University, Atlanta, Georgia 30322, USA.
Ainsley
A
Nicholson
Rebecca M
RM
Fabbri
Jason W
JW
Reeves
Gray F
GF
Crouse
D020137:Base Pair Mismatch; D001483:Base Sequence; D015825:Chromosomes, Fungal / Q000235:genetics; D003434:Crossing Over, Genetic; D004260:DNA Repair / Q000235:genetics*; D045643:DNA Repair Enzymes; D004271:DNA, Fungal / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D015252:Deoxyribonucleases, Type II Site-Specific / Q000235:genetics / Q000378:metabolism; D004720:Endonucleases / Q000235:genetics*; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D005800:Genes, Fungal; D007438:Introns; D008957:Models, Genetic; D051718:MutS Homolog 2 Protein / Q000235:genetics / Q000378:metabolism; D000074081:MutS Homolog 3 Protein; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism; D013379:Substrate Specificity
D004271:DNA, Fungal; D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C081696:MSH3 protein, S cerevisiae; D000074081:MutS Homolog 3 Protein; D029701:Saccharomyces cerevisiae Proteins; D004720:Endonucleases; C069266:RAD1 protein, S cerevisiae; C530845:HO protein, S cerevisiae; C037725:SCEI protein, S cerevisiae; D015252:Deoxyribonucleases, Type II Site-Specific; C489751:MSH2 protein, S cerevisiae; D051718:MutS Homolog 2 Protein; D045643:DNA Repair Enzymes