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Genome-wide high-resolution mapping of UV-induced mitotic recombination events in Saccharomyces cerevisiae.

Yin Y, Petes TD - PLoS Genet. (2013)

Bottom Line: Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH).UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells.Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR) events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
In the yeast Saccharomyces cerevisiae and most other eukaryotes, mitotic recombination is important for the repair of double-stranded DNA breaks (DSBs). Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH). In this study, LOH events induced by ultraviolet (UV) light are mapped throughout the genome to a resolution of about 1 kb using single-nucleotide polymorphism (SNP) microarrays. UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells. In addition, UV stimulates recombination in G1-synchronized cells about 10-fold more efficiently than in G2-synchronized cells. Importantly, at high doses of UV, most conversion events reflect the repair of two sister chromatids that are broken at approximately the same position whereas at low doses, most conversion events reflect the repair of a single broken chromatid. Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR) events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

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Common patterns of conversions and crossovers derived from UV-treated cells.The key is described in Figure 4C. A. Simple crossover unassociated with conversion. B. Crossover associated with a 3∶1 conversion event. C. Crossover associated with a 3∶1/4∶0 hybrid conversion tract. D. Complex crossover/conversion event. E. 3∶1 conversion unassociated with a crossover. F. BIR event.
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pgen-1003894-g005: Common patterns of conversions and crossovers derived from UV-treated cells.The key is described in Figure 4C. A. Simple crossover unassociated with conversion. B. Crossover associated with a 3∶1 conversion event. C. Crossover associated with a 3∶1/4∶0 hybrid conversion tract. D. Complex crossover/conversion event. E. 3∶1 conversion unassociated with a crossover. F. BIR event.

Mentions: Most (41 of 45) of the selected crossovers were associated with gene conversion events. In Figure 5, we show some of the common LOH patterns observed for the selected crossovers as well as for unselected recombination events. These depictions include a crossover unassociated with gene conversion (Figure 5A), a crossover associated with a 3∶1 conversion event (Figure 5B), a crossover associated with a 3∶1/4∶0 hybrid tract (Figure 5C), a crossover associated with a complex conversion tract (Figure 5D), a 3∶1 conversion unassociated with a crossover (Figure 5E), and a BIR event (Figure 5F). It should be noted that the patterns of gene conversion in sectored colonies can be used to infer which homolog was broken to initiate the recombination event. A chromosome that receives a DSB acts as a recipient during gene conversion [4]. Thus, in the event shown in Figure 5B, in which there is a red segment opposite a green segment, we can infer that the event was initiated by breaking the YJM789-derived (black) homolog.


Genome-wide high-resolution mapping of UV-induced mitotic recombination events in Saccharomyces cerevisiae.

Yin Y, Petes TD - PLoS Genet. (2013)

Common patterns of conversions and crossovers derived from UV-treated cells.The key is described in Figure 4C. A. Simple crossover unassociated with conversion. B. Crossover associated with a 3∶1 conversion event. C. Crossover associated with a 3∶1/4∶0 hybrid conversion tract. D. Complex crossover/conversion event. E. 3∶1 conversion unassociated with a crossover. F. BIR event.
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Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC3814309&req=5

pgen-1003894-g005: Common patterns of conversions and crossovers derived from UV-treated cells.The key is described in Figure 4C. A. Simple crossover unassociated with conversion. B. Crossover associated with a 3∶1 conversion event. C. Crossover associated with a 3∶1/4∶0 hybrid conversion tract. D. Complex crossover/conversion event. E. 3∶1 conversion unassociated with a crossover. F. BIR event.
Mentions: Most (41 of 45) of the selected crossovers were associated with gene conversion events. In Figure 5, we show some of the common LOH patterns observed for the selected crossovers as well as for unselected recombination events. These depictions include a crossover unassociated with gene conversion (Figure 5A), a crossover associated with a 3∶1 conversion event (Figure 5B), a crossover associated with a 3∶1/4∶0 hybrid tract (Figure 5C), a crossover associated with a complex conversion tract (Figure 5D), a 3∶1 conversion unassociated with a crossover (Figure 5E), and a BIR event (Figure 5F). It should be noted that the patterns of gene conversion in sectored colonies can be used to infer which homolog was broken to initiate the recombination event. A chromosome that receives a DSB acts as a recipient during gene conversion [4]. Thus, in the event shown in Figure 5B, in which there is a red segment opposite a green segment, we can infer that the event was initiated by breaking the YJM789-derived (black) homolog.

Bottom Line: Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH).UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells.Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR) events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

View Article: PubMed Central - PubMed

Affiliation: Department of Molecular Genetics and Microbiology and University Program in Genetics and Genomics, Duke University Medical Center, Durham, North Carolina, United States of America.

ABSTRACT
In the yeast Saccharomyces cerevisiae and most other eukaryotes, mitotic recombination is important for the repair of double-stranded DNA breaks (DSBs). Mitotic recombination between homologous chromosomes can result in loss of heterozygosity (LOH). In this study, LOH events induced by ultraviolet (UV) light are mapped throughout the genome to a resolution of about 1 kb using single-nucleotide polymorphism (SNP) microarrays. UV doses that have little effect on the viability of diploid cells stimulate crossovers more than 1000-fold in wild-type cells. In addition, UV stimulates recombination in G1-synchronized cells about 10-fold more efficiently than in G2-synchronized cells. Importantly, at high doses of UV, most conversion events reflect the repair of two sister chromatids that are broken at approximately the same position whereas at low doses, most conversion events reflect the repair of a single broken chromatid. Genome-wide mapping of about 380 unselected crossovers, break-induced replication (BIR) events, and gene conversions shows that UV-induced recombination events occur throughout the genome without pronounced hotspots, although the ribosomal RNA gene cluster has a significantly lower frequency of crossovers.

Show MeSH
Related in: MedlinePlus