The relationship between homology length and crossing over during the repair of a broken chromosome.
Homologous recombination can result in the transfer of genetic information from one DNA molecule to another (gene conversion). These events are often accompanied by a reciprocal exchange between the interacting molecules (termed "crossing over"). This association suggests that the two types of events could be mechanistically related. We have analyzed the repair, by homologous recombination, of a broken chromosome in yeast. We show that gene conversion can be uncoupled from crossing over when the length of homology of the interacting substrates is below a certain threshold. In addition, a minimal length of homology on each broken chromosomal arm is needed for crossing over. We also show that the coupling between gene conversion and crossing over is affected by the mismatch repair system; mutations in the MSH2 or MSH6 genes cause an increase in the crossing over observed for short alleles. Our results provide a mechanism to explain how chromosomal recombinational repair can take place without altering the stability of the genome.
Department of Molecular Microbiology and Biotechnology, Tel Aviv University, Ramat Aviv 69978, Israel.
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Inbar
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Liefshitz
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Bitan
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Kupiec
D000483:Alleles; D020137:Base Pair Mismatch; D015139:Blotting, Southern; D002875:Chromosomes; D003434:Crossing Over, Genetic; D004260:DNA Repair; D004262:DNA Restriction Enzymes / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics; D005656:Fungal Proteins / Q000235:genetics; D005785:Gene Conversion; D007700:Kinetics; D008957:Models, Genetic; D051718:MutS Homolog 2 Protein; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D010957:Plasmids / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins; D013997:Time Factors
D004268:DNA-Binding Proteins; D005656:Fungal Proteins; C098790:MSH6 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D004262:DNA Restriction Enzymes; C489751:MSH2 protein, S cerevisiae; D051718:MutS Homolog 2 Protein