Limits...
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.

Show MeSH

Related in: MedlinePlus

Mechanisms of homologous recombination.The two interacting DNA molecules are shown as double-stranded. The recombination event is initiated by a double-stranded DNA break (DSB) on the black molecule, and the broken ends are resected 5′ to 3′. In this depiction, the left processed end invades the red molecule, forming a heteroduplex. Dotted lines show DNA synthesis associated with the recombination event. A. Synthesis-dependent strand annealing (SDSA). The 3′ end of the invading strand is used as a primer for DNA synthesis, extending the D-loop. Dissociation of the D-loop, followed by re-annealing of the two broken ends results in a region of heteroduplex (outlined in blue) with flanking markers in the parental non-crossover (NCO) configuration. B. Double-strand break repair (DSBR). Following expansion of the D-loop, pairing occurs between the displaced strand and the right end of the broken chromosome, resulting in two regions of heteroduplex. The resulting double Holliday junction can be resolved by topoisomerase-mediated dissolution or by cleavage of the Holliday junctions to yield an NCO or a crossover (CO). C. Break-induced replication (BIR). In this pathway, the right broken chromosome is lost and the left molecule invades the homologous chromosome, resulting in duplication of sequences distal to the point of invasion.
© Copyright Policy
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC3814309&req=5

pgen-1003894-g001: Mechanisms of homologous recombination.The two interacting DNA molecules are shown as double-stranded. The recombination event is initiated by a double-stranded DNA break (DSB) on the black molecule, and the broken ends are resected 5′ to 3′. In this depiction, the left processed end invades the red molecule, forming a heteroduplex. Dotted lines show DNA synthesis associated with the recombination event. A. Synthesis-dependent strand annealing (SDSA). The 3′ end of the invading strand is used as a primer for DNA synthesis, extending the D-loop. Dissociation of the D-loop, followed by re-annealing of the two broken ends results in a region of heteroduplex (outlined in blue) with flanking markers in the parental non-crossover (NCO) configuration. B. Double-strand break repair (DSBR). Following expansion of the D-loop, pairing occurs between the displaced strand and the right end of the broken chromosome, resulting in two regions of heteroduplex. The resulting double Holliday junction can be resolved by topoisomerase-mediated dissolution or by cleavage of the Holliday junctions to yield an NCO or a crossover (CO). C. Break-induced replication (BIR). In this pathway, the right broken chromosome is lost and the left molecule invades the homologous chromosome, resulting in duplication of sequences distal to the point of invasion.

Mentions: DSBs can be repaired by a number of different HR pathways [5]. For all of these pathways, the broken DNA ends are processed by 5′ to 3′ degradation, followed by invasion of the processed chromosome end into either a sister chromatid or a homolog (Figure 1). In the synthesis-dependent strand annealing (SDSA) pathway, after strand invasion and DNA synthesis, the invading broken end is displaced and reanneals to the other broken end. The resulting product has a region of heteroduplex DNA and mismatches within the heteroduplex can be repaired to yield a gene conversion event unassociated with a crossover (Figure 1A). Alternatively, the broken ends can both engage in pairing with the intact chromosome resulting in a double Holliday junction (Figure 1B). This structure can be resolved to yield a crossover or non-crossover. As in the SDSA pathway, mismatches within the heteroduplex region can be repaired to generate a conversion event. Lastly, invasion of one broken end can result in the generation of a replication structure that duplicates sequences from the other chromosome from the point of invasion to the end of the chromosome (break-induced replication, BIR; Figure 1C).


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

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

Mechanisms of homologous recombination.The two interacting DNA molecules are shown as double-stranded. The recombination event is initiated by a double-stranded DNA break (DSB) on the black molecule, and the broken ends are resected 5′ to 3′. In this depiction, the left processed end invades the red molecule, forming a heteroduplex. Dotted lines show DNA synthesis associated with the recombination event. A. Synthesis-dependent strand annealing (SDSA). The 3′ end of the invading strand is used as a primer for DNA synthesis, extending the D-loop. Dissociation of the D-loop, followed by re-annealing of the two broken ends results in a region of heteroduplex (outlined in blue) with flanking markers in the parental non-crossover (NCO) configuration. B. Double-strand break repair (DSBR). Following expansion of the D-loop, pairing occurs between the displaced strand and the right end of the broken chromosome, resulting in two regions of heteroduplex. The resulting double Holliday junction can be resolved by topoisomerase-mediated dissolution or by cleavage of the Holliday junctions to yield an NCO or a crossover (CO). C. Break-induced replication (BIR). In this pathway, the right broken chromosome is lost and the left molecule invades the homologous chromosome, resulting in duplication of sequences distal to the point of invasion.
© Copyright Policy
Related In: Results  -  Collection

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

pgen-1003894-g001: Mechanisms of homologous recombination.The two interacting DNA molecules are shown as double-stranded. The recombination event is initiated by a double-stranded DNA break (DSB) on the black molecule, and the broken ends are resected 5′ to 3′. In this depiction, the left processed end invades the red molecule, forming a heteroduplex. Dotted lines show DNA synthesis associated with the recombination event. A. Synthesis-dependent strand annealing (SDSA). The 3′ end of the invading strand is used as a primer for DNA synthesis, extending the D-loop. Dissociation of the D-loop, followed by re-annealing of the two broken ends results in a region of heteroduplex (outlined in blue) with flanking markers in the parental non-crossover (NCO) configuration. B. Double-strand break repair (DSBR). Following expansion of the D-loop, pairing occurs between the displaced strand and the right end of the broken chromosome, resulting in two regions of heteroduplex. The resulting double Holliday junction can be resolved by topoisomerase-mediated dissolution or by cleavage of the Holliday junctions to yield an NCO or a crossover (CO). C. Break-induced replication (BIR). In this pathway, the right broken chromosome is lost and the left molecule invades the homologous chromosome, resulting in duplication of sequences distal to the point of invasion.
Mentions: DSBs can be repaired by a number of different HR pathways [5]. For all of these pathways, the broken DNA ends are processed by 5′ to 3′ degradation, followed by invasion of the processed chromosome end into either a sister chromatid or a homolog (Figure 1). In the synthesis-dependent strand annealing (SDSA) pathway, after strand invasion and DNA synthesis, the invading broken end is displaced and reanneals to the other broken end. The resulting product has a region of heteroduplex DNA and mismatches within the heteroduplex can be repaired to yield a gene conversion event unassociated with a crossover (Figure 1A). Alternatively, the broken ends can both engage in pairing with the intact chromosome resulting in a double Holliday junction (Figure 1B). This structure can be resolved to yield a crossover or non-crossover. As in the SDSA pathway, mismatches within the heteroduplex region can be repaired to generate a conversion event. Lastly, invasion of one broken end can result in the generation of a replication structure that duplicates sequences from the other chromosome from the point of invasion to the end of the chromosome (break-induced replication, BIR; Figure 1C).

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