Limits...
The role of Exo1p exonuclease in DNA end resection to generate gene conversion tracts in Saccharomyces cerevisiae.

Yin Y, Petes TD - Genetics (2014)

Bottom Line: In accordance with this expectation, gene conversion tract lengths associated with spontaneous crossovers in exo1 strains were reduced about twofold relative to wild type.For UV-induced events, conversion tract lengths associated with crossovers were also shorter for the exo1 strain than for the wild-type strain (3.2 and 7.6 kb, respectively).Unexpectedly, however, the lengths of conversion tracts that were unassociated with crossovers were longer in the exo1 strain than in the wild-type strain (6.2 and 4.8 kb, respectively).

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 27710.

Show MeSH

Related in: MedlinePlus

Patterns of crossover-associated and crossover-unassociated conversion tracts based on current models of recombination. Black and red lines show DNA strands of the two homologs with arrows marking the 3′ ends. Dotted lines show repair-associated DNA synthesis. For all of the models, we assume that conversion events unassociated with crossovers (NCO) occur as a consequence of SDSA, and events associated with crossovers (CO) reflect resolution of Holliday junctions. We assume that the two broken ends are resected to the same extent (AWT = BWT), although our conclusions do not require this assumption (details in text). CWT shows the length of DNA synthesized by the invading strand. In heteroduplexes with one black strand and one red strand, we show correction of the mismatches to generate two red strands. The resulting conversion tracts are outlined in blue. (A) The length of DNA synthesized by the invading strand (CWT) equals the amount of resection, and AWT = BWT. The expected conversion tract length for events associated with crossovers is about twice that for events unassociated with crossovers. (B) If CWT < AWT and BWT, then the relative length of the crossover-associated tract compared to the crossover-unassociated tract is greater than in A. (C) If CWT > AWT and BWT, one possibility is that, during the SDSA event, the 3′ end of the reinvading strand is displaced. Removal of this end by a branch-processing enzyme such as Rad1p/Rad10p (Mazón et al. 2012) would result in a conversion tract in the NCO pathway that is the same length as in A.
© Copyright Policy - open-access
Related In: Results  -  Collection


getmorefigures.php?uid=PMC4125386&req=5

fig6: Patterns of crossover-associated and crossover-unassociated conversion tracts based on current models of recombination. Black and red lines show DNA strands of the two homologs with arrows marking the 3′ ends. Dotted lines show repair-associated DNA synthesis. For all of the models, we assume that conversion events unassociated with crossovers (NCO) occur as a consequence of SDSA, and events associated with crossovers (CO) reflect resolution of Holliday junctions. We assume that the two broken ends are resected to the same extent (AWT = BWT), although our conclusions do not require this assumption (details in text). CWT shows the length of DNA synthesized by the invading strand. In heteroduplexes with one black strand and one red strand, we show correction of the mismatches to generate two red strands. The resulting conversion tracts are outlined in blue. (A) The length of DNA synthesized by the invading strand (CWT) equals the amount of resection, and AWT = BWT. The expected conversion tract length for events associated with crossovers is about twice that for events unassociated with crossovers. (B) If CWT < AWT and BWT, then the relative length of the crossover-associated tract compared to the crossover-unassociated tract is greater than in A. (C) If CWT > AWT and BWT, one possibility is that, during the SDSA event, the 3′ end of the reinvading strand is displaced. Removal of this end by a branch-processing enzyme such as Rad1p/Rad10p (Mazón et al. 2012) would result in a conversion tract in the NCO pathway that is the same length as in A.

Mentions: In depictions of the double-strand break repair model, the extent of the gene conversion tract is usually shown as equivalent to the extent of end resection (Figure 6A). For a recombination event in a wild-type strand, we indicate the resection length of the invading chromosome end as AWT and the resection length of the other end as BWT, and the simplest assumption is that AWT = BWT. Further, we hypothesize that amount of DNA synthesized by the invading end (CWT) is equivalent to the resection length. With these assumptions, one would expect that the length of gene conversion tracts unassociated with crossovers would be half of that associated with crossovers. In addition, we would expect both types of conversion tracts would be shorter in the exo1 strain because of less resection. If AWT and BWT are not equal, nonetheless, the conversion tracts unassociated with crossovers would be expected to be shorter than those associated with crossovers.


The role of Exo1p exonuclease in DNA end resection to generate gene conversion tracts in Saccharomyces cerevisiae.

Yin Y, Petes TD - Genetics (2014)

Patterns of crossover-associated and crossover-unassociated conversion tracts based on current models of recombination. Black and red lines show DNA strands of the two homologs with arrows marking the 3′ ends. Dotted lines show repair-associated DNA synthesis. For all of the models, we assume that conversion events unassociated with crossovers (NCO) occur as a consequence of SDSA, and events associated with crossovers (CO) reflect resolution of Holliday junctions. We assume that the two broken ends are resected to the same extent (AWT = BWT), although our conclusions do not require this assumption (details in text). CWT shows the length of DNA synthesized by the invading strand. In heteroduplexes with one black strand and one red strand, we show correction of the mismatches to generate two red strands. The resulting conversion tracts are outlined in blue. (A) The length of DNA synthesized by the invading strand (CWT) equals the amount of resection, and AWT = BWT. The expected conversion tract length for events associated with crossovers is about twice that for events unassociated with crossovers. (B) If CWT < AWT and BWT, then the relative length of the crossover-associated tract compared to the crossover-unassociated tract is greater than in A. (C) If CWT > AWT and BWT, one possibility is that, during the SDSA event, the 3′ end of the reinvading strand is displaced. Removal of this end by a branch-processing enzyme such as Rad1p/Rad10p (Mazón et al. 2012) would result in a conversion tract in the NCO pathway that is the same length as in A.
© Copyright Policy - open-access
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4125386&req=5

fig6: Patterns of crossover-associated and crossover-unassociated conversion tracts based on current models of recombination. Black and red lines show DNA strands of the two homologs with arrows marking the 3′ ends. Dotted lines show repair-associated DNA synthesis. For all of the models, we assume that conversion events unassociated with crossovers (NCO) occur as a consequence of SDSA, and events associated with crossovers (CO) reflect resolution of Holliday junctions. We assume that the two broken ends are resected to the same extent (AWT = BWT), although our conclusions do not require this assumption (details in text). CWT shows the length of DNA synthesized by the invading strand. In heteroduplexes with one black strand and one red strand, we show correction of the mismatches to generate two red strands. The resulting conversion tracts are outlined in blue. (A) The length of DNA synthesized by the invading strand (CWT) equals the amount of resection, and AWT = BWT. The expected conversion tract length for events associated with crossovers is about twice that for events unassociated with crossovers. (B) If CWT < AWT and BWT, then the relative length of the crossover-associated tract compared to the crossover-unassociated tract is greater than in A. (C) If CWT > AWT and BWT, one possibility is that, during the SDSA event, the 3′ end of the reinvading strand is displaced. Removal of this end by a branch-processing enzyme such as Rad1p/Rad10p (Mazón et al. 2012) would result in a conversion tract in the NCO pathway that is the same length as in A.
Mentions: In depictions of the double-strand break repair model, the extent of the gene conversion tract is usually shown as equivalent to the extent of end resection (Figure 6A). For a recombination event in a wild-type strand, we indicate the resection length of the invading chromosome end as AWT and the resection length of the other end as BWT, and the simplest assumption is that AWT = BWT. Further, we hypothesize that amount of DNA synthesized by the invading end (CWT) is equivalent to the resection length. With these assumptions, one would expect that the length of gene conversion tracts unassociated with crossovers would be half of that associated with crossovers. In addition, we would expect both types of conversion tracts would be shorter in the exo1 strain because of less resection. If AWT and BWT are not equal, nonetheless, the conversion tracts unassociated with crossovers would be expected to be shorter than those associated with crossovers.

Bottom Line: In accordance with this expectation, gene conversion tract lengths associated with spontaneous crossovers in exo1 strains were reduced about twofold relative to wild type.For UV-induced events, conversion tract lengths associated with crossovers were also shorter for the exo1 strain than for the wild-type strain (3.2 and 7.6 kb, respectively).Unexpectedly, however, the lengths of conversion tracts that were unassociated with crossovers were longer in the exo1 strain than in the wild-type strain (6.2 and 4.8 kb, respectively).

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 27710.

Show MeSH
Related in: MedlinePlus