Limits...
Frequent and efficient use of the sister chromatid for DNA double-strand break repair during budding yeast meiosis.

Goldfarb T, Lichten M - PLoS Biol. (2010)

Bottom Line: This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold) yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies.These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids.We suggest that a Mek1-dependent reduction in the rate of inter-sister repair, combined with the destabilization of inter-sister JMs, promotes inter-homolog recombination while retaining the capacity for inter-sister recombination when inter-homolog recombination is not possible.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.

ABSTRACT
Recombination between homologous chromosomes of different parental origin (homologs) is necessary for their accurate segregation during meiosis. It has been suggested that meiotic inter-homolog recombination is promoted by a barrier to inter-sister-chromatid recombination, imposed by meiosis-specific components of the chromosome axis. Consistent with this, measures of Holliday junction-containing recombination intermediates (joint molecules [JMs]) show a strong bias towards inter-homolog and against inter-sister JMs. However, recombination between sister chromatids also has an important role in meiosis. The genomes of diploid organisms in natural populations are highly polymorphic for insertions and deletions, and meiotic double-strand breaks (DSBs) that form within such polymorphic regions must be repaired by inter-sister recombination. Efforts to study inter-sister recombination during meiosis, in particular to determine recombination frequencies and mechanisms, have been constrained by the inability to monitor the products of inter-sister recombination. We present here molecular-level studies of inter-sister recombination during budding yeast meiosis. We examined events initiated by DSBs in regions that lack corresponding sequences on the homolog, and show that these DSBs are efficiently repaired by inter-sister recombination. This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold) yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies. Furthermore, inter-sister JMs formed in mek1Δ mutants are preferentially lost, while inter-homolog JMs are maintained. These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids. We suggest that a Mek1-dependent reduction in the rate of inter-sister repair, combined with the destabilization of inter-sister JMs, promotes inter-homolog recombination while retaining the capacity for inter-sister recombination when inter-homolog recombination is not possible.

Show MeSH

Related in: MedlinePlus

DSBs at a hemizygous locus do not alter nuclear division timing or spore viability.(A) Timing of the meiosis I nuclear division, monitored by DAPI staining (see Protocol S1). Values are the average of 3–4 experiments (error bars indicate standard deviation). RAD50 strains as in Figure 1. (B) Spore viability in tetrads in the indicated strains. NMS indicates non-Mendelian segregation (full conversion and post-meiotic segregation) at the his4::URA3-arg4 insert. The strain homozygous for the insert (MJL3195) is a his4::URA3-arg4-pal/his4::ura3-pal-ARG4 trans-heterozygote. Non-Mendelian segregation at ura3-pal and at arg4-pal were scored; non-Mendelian segregation for both markers in the same tetrad was scored as a single event. In the his4::URA3-arg4 hemizygote (MJL3192), non-Mendelian segregation events involved loss (1∶3) or gain (3∶1) of the URA3-arg4 insert.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2957403&req=5

pbio-1000520-g002: DSBs at a hemizygous locus do not alter nuclear division timing or spore viability.(A) Timing of the meiosis I nuclear division, monitored by DAPI staining (see Protocol S1). Values are the average of 3–4 experiments (error bars indicate standard deviation). RAD50 strains as in Figure 1. (B) Spore viability in tetrads in the indicated strains. NMS indicates non-Mendelian segregation (full conversion and post-meiotic segregation) at the his4::URA3-arg4 insert. The strain homozygous for the insert (MJL3195) is a his4::URA3-arg4-pal/his4::ura3-pal-ARG4 trans-heterozygote. Non-Mendelian segregation at ura3-pal and at arg4-pal were scored; non-Mendelian segregation for both markers in the same tetrad was scored as a single event. In the his4::URA3-arg4 hemizygote (MJL3192), non-Mendelian segregation events involved loss (1∶3) or gain (3∶1) of the URA3-arg4 insert.

Mentions: A BSCR-induced delay in DSB repair at a hemizygous site might cause a DNA-damage-response-induced delay in the MI division. We did not observe a significant difference between his4::URA3-arg4 or YCR047c hemizygotes and fully homozygous controls for meiotic division timing or for the fraction of cells that transited meiotic divisions (Figure 2A; data not shown). In addition, no loss of spore viability was observed in strains hemizygous for the his4::URA3-arg4 insert (Figure 2B), as might be expected if an unrepaired DSB persisted through meiotic divisions and sporulation.


Frequent and efficient use of the sister chromatid for DNA double-strand break repair during budding yeast meiosis.

Goldfarb T, Lichten M - PLoS Biol. (2010)

DSBs at a hemizygous locus do not alter nuclear division timing or spore viability.(A) Timing of the meiosis I nuclear division, monitored by DAPI staining (see Protocol S1). Values are the average of 3–4 experiments (error bars indicate standard deviation). RAD50 strains as in Figure 1. (B) Spore viability in tetrads in the indicated strains. NMS indicates non-Mendelian segregation (full conversion and post-meiotic segregation) at the his4::URA3-arg4 insert. The strain homozygous for the insert (MJL3195) is a his4::URA3-arg4-pal/his4::ura3-pal-ARG4 trans-heterozygote. Non-Mendelian segregation at ura3-pal and at arg4-pal were scored; non-Mendelian segregation for both markers in the same tetrad was scored as a single event. In the his4::URA3-arg4 hemizygote (MJL3192), non-Mendelian segregation events involved loss (1∶3) or gain (3∶1) of the URA3-arg4 insert.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2957403&req=5

pbio-1000520-g002: DSBs at a hemizygous locus do not alter nuclear division timing or spore viability.(A) Timing of the meiosis I nuclear division, monitored by DAPI staining (see Protocol S1). Values are the average of 3–4 experiments (error bars indicate standard deviation). RAD50 strains as in Figure 1. (B) Spore viability in tetrads in the indicated strains. NMS indicates non-Mendelian segregation (full conversion and post-meiotic segregation) at the his4::URA3-arg4 insert. The strain homozygous for the insert (MJL3195) is a his4::URA3-arg4-pal/his4::ura3-pal-ARG4 trans-heterozygote. Non-Mendelian segregation at ura3-pal and at arg4-pal were scored; non-Mendelian segregation for both markers in the same tetrad was scored as a single event. In the his4::URA3-arg4 hemizygote (MJL3192), non-Mendelian segregation events involved loss (1∶3) or gain (3∶1) of the URA3-arg4 insert.
Mentions: A BSCR-induced delay in DSB repair at a hemizygous site might cause a DNA-damage-response-induced delay in the MI division. We did not observe a significant difference between his4::URA3-arg4 or YCR047c hemizygotes and fully homozygous controls for meiotic division timing or for the fraction of cells that transited meiotic divisions (Figure 2A; data not shown). In addition, no loss of spore viability was observed in strains hemizygous for the his4::URA3-arg4 insert (Figure 2B), as might be expected if an unrepaired DSB persisted through meiotic divisions and sporulation.

Bottom Line: This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold) yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies.These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids.We suggest that a Mek1-dependent reduction in the rate of inter-sister repair, combined with the destabilization of inter-sister JMs, promotes inter-homolog recombination while retaining the capacity for inter-sister recombination when inter-homolog recombination is not possible.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Biochemistry and Molecular Biology, Center for Cancer Research, National Cancer Institute, Bethesda, Maryland, United States of America.

ABSTRACT
Recombination between homologous chromosomes of different parental origin (homologs) is necessary for their accurate segregation during meiosis. It has been suggested that meiotic inter-homolog recombination is promoted by a barrier to inter-sister-chromatid recombination, imposed by meiosis-specific components of the chromosome axis. Consistent with this, measures of Holliday junction-containing recombination intermediates (joint molecules [JMs]) show a strong bias towards inter-homolog and against inter-sister JMs. However, recombination between sister chromatids also has an important role in meiosis. The genomes of diploid organisms in natural populations are highly polymorphic for insertions and deletions, and meiotic double-strand breaks (DSBs) that form within such polymorphic regions must be repaired by inter-sister recombination. Efforts to study inter-sister recombination during meiosis, in particular to determine recombination frequencies and mechanisms, have been constrained by the inability to monitor the products of inter-sister recombination. We present here molecular-level studies of inter-sister recombination during budding yeast meiosis. We examined events initiated by DSBs in regions that lack corresponding sequences on the homolog, and show that these DSBs are efficiently repaired by inter-sister recombination. This occurs with the same timing as inter-homolog recombination, but with reduced (2- to 3-fold) yields of JMs. Loss of the meiotic-chromosome-axis-associated kinase Mek1 accelerates inter-sister DSB repair and markedly increases inter-sister JM frequencies. Furthermore, inter-sister JMs formed in mek1Δ mutants are preferentially lost, while inter-homolog JMs are maintained. These findings indicate that inter-sister recombination occurs frequently during budding yeast meiosis, with the possibility that up to one-third of all recombination events occur between sister chromatids. We suggest that a Mek1-dependent reduction in the rate of inter-sister repair, combined with the destabilization of inter-sister JMs, promotes inter-homolog recombination while retaining the capacity for inter-sister recombination when inter-homolog recombination is not possible.

Show MeSH
Related in: MedlinePlus