Mitotic gene conversion tracts associated with repair of a defined double-strand break inSaccharomyces cerevisiae
| Autor: | Yee Fang Hum, Sue Jinks-Robertson |
|---|---|
| Rok vydání: | 2017 |
| Předmět: |
0301 basic medicine
Mitotic crossover Crossover Saccharomyces cerevisiae Gene Conversion Mitosis Investigations Loss of heterozygosity 03 medical and health sciences 0302 clinical medicine Genetics Homologous chromosome DNA Breaks Double-Stranded Crossing Over Genetic Gene conversion biology Recombinational DNA Repair Chromosome biology.organism_classification 030104 developmental biology DNA mismatch repair Chromatid DNA microarray Homologous recombination 030217 neurology & neurosurgery Heteroduplex |
| Popis: | Mitotic recombination between homologous chromosomes leads to the uncovering of recessive alleles through loss of heterozygosity. In the current study, a defined double-strand break was used to initiate reciprocal loss of heterozygosity between diverged homologs of chromosome IV in Saccharomyces cerevisiae. These events resulted from the repair of two broken chromatids, one of which was repaired as a crossover and the other as a noncrossover. Associated gene conversion tracts resulting from the donor-directed repair of mismatches formed during strand exchange (heteroduplex DNA) were mapped using microarrays. Gene conversion tracts associated with individual crossover and noncrossover events were similar in size and position, with half of the tracts being unidirectional and mapping to only one side of the initiating break. Among crossover events, this likely reflected gene conversion on only one side of the break, with restoration-type repair occurring on the other side. For noncrossover events, an ectopic system was used to directly compare gene conversion tracts produced in a wild-type strain to heteroduplex DNA tracts generated in the absence of the Mlh1 mismatch-repair protein. There was a strong bias for unidirectional tracts in the absence, but not in the presence, of Mlh1. This suggests that mismatch repair acts on heteroduplex DNA that is only transiently present in noncrossover intermediates of the synthesis dependent strand annealing pathway. Although the molecular features of events associated with loss of heterozygosity generally agreed with those predicted by current recombination models, there were unexpected complexities in associated gene conversion tracts. |
| Databáze: | OpenAIRE |
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