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Different roles of eukaryotic MutS and MutL complexes in repair of small insertion and deletion loops in yeast.

Romanova NV, Crouse GF - PLoS Genet. (2013)

Bottom Line: Upon recognition of a mispair, the MutS complexes then interact with homologues of the bacterial MutL protein.Loops formed on the primer strand during replication lead to insertion mutations, whereas loops on the template strand lead to deletions.MutSβ is present in many eukaryotic organisms, but not in prokaryotes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
DNA mismatch repair greatly increases genome fidelity by recognizing and removing replication errors. In order to understand how this fidelity is maintained, it is important to uncover the relative specificities of the different components of mismatch repair. There are two major mispair recognition complexes in eukaryotes that are homologues of bacterial MutS proteins, MutSα and MutSβ, with MutSα recognizing base-base mismatches and small loop mispairs and MutSβ recognizing larger loop mispairs. Upon recognition of a mispair, the MutS complexes then interact with homologues of the bacterial MutL protein. Loops formed on the primer strand during replication lead to insertion mutations, whereas loops on the template strand lead to deletions. We show here in yeast, using oligonucleotide transformation, that MutSα has a strong bias toward repair of insertion loops, while MutSβ has an even stronger bias toward repair of deletion loops. Our results suggest that this bias in repair is due to the different interactions of the MutS complexes with the MutL complexes. Two mutants of MutLα, pms1-G882E and pms1-H888R, repair deletion mispairs but not insertion mispairs. Moreover, we find that a different MutL complex, MutLγ, is extremely important, but not sufficient, for deletion repair in the presence of either MutLα mutation. MutSβ is present in many eukaryotic organisms, but not in prokaryotes. We suggest that the biased repair of deletion mispairs may reflect a critical eukaryotic function of MutSβ in mismatch repair.

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Related in: MedlinePlus

Effect of MMR on 1-nt in/del mismatches.TrL1 Oligos were transformed into Same-orientation strains of the indicated genotypes and analyzed as in Figure 2 (TrL1-Lag-s). For 1-nt in/del mismatches, oligos creating insertion loops are transformed into lys2ΔA746 strains and oligos creating deletion loops are transformed into lys2ΔBgl strains. Only MutSβ is present in msh6 strains and only MutSα is present in msh3 strains.
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pgen-1003920-g004: Effect of MMR on 1-nt in/del mismatches.TrL1 Oligos were transformed into Same-orientation strains of the indicated genotypes and analyzed as in Figure 2 (TrL1-Lag-s). For 1-nt in/del mismatches, oligos creating insertion loops are transformed into lys2ΔA746 strains and oligos creating deletion loops are transformed into lys2ΔBgl strains. Only MutSβ is present in msh6 strains and only MutSα is present in msh3 strains.

Mentions: Previously, the evidence for the differential effect of MutSα and MutSβ on in/del mutations came from a dinucleotide repeat assay, although an assay using one particular mononucleotide repeat indicated that the loss of either MutSα or MutSβ led to an increase mainly of deletions [18]. The pms1-G882E and pms1-H888R mutations had only been examined with mononucleotide repeats [22]. Therefore we wanted to examine whether the effects we observed on 2-nt in/del mispairs would be observed in similar 1-nt in/del mismatches. For that survey, we used only oligos in one location, and the results are presented in Figures 4 and S3; quantitative comparisons are given in Table 3.


Different roles of eukaryotic MutS and MutL complexes in repair of small insertion and deletion loops in yeast.

Romanova NV, Crouse GF - PLoS Genet. (2013)

Effect of MMR on 1-nt in/del mismatches.TrL1 Oligos were transformed into Same-orientation strains of the indicated genotypes and analyzed as in Figure 2 (TrL1-Lag-s). For 1-nt in/del mismatches, oligos creating insertion loops are transformed into lys2ΔA746 strains and oligos creating deletion loops are transformed into lys2ΔBgl strains. Only MutSβ is present in msh6 strains and only MutSα is present in msh3 strains.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3814323&req=5

pgen-1003920-g004: Effect of MMR on 1-nt in/del mismatches.TrL1 Oligos were transformed into Same-orientation strains of the indicated genotypes and analyzed as in Figure 2 (TrL1-Lag-s). For 1-nt in/del mismatches, oligos creating insertion loops are transformed into lys2ΔA746 strains and oligos creating deletion loops are transformed into lys2ΔBgl strains. Only MutSβ is present in msh6 strains and only MutSα is present in msh3 strains.
Mentions: Previously, the evidence for the differential effect of MutSα and MutSβ on in/del mutations came from a dinucleotide repeat assay, although an assay using one particular mononucleotide repeat indicated that the loss of either MutSα or MutSβ led to an increase mainly of deletions [18]. The pms1-G882E and pms1-H888R mutations had only been examined with mononucleotide repeats [22]. Therefore we wanted to examine whether the effects we observed on 2-nt in/del mispairs would be observed in similar 1-nt in/del mismatches. For that survey, we used only oligos in one location, and the results are presented in Figures 4 and S3; quantitative comparisons are given in Table 3.

Bottom Line: Upon recognition of a mispair, the MutS complexes then interact with homologues of the bacterial MutL protein.Loops formed on the primer strand during replication lead to insertion mutations, whereas loops on the template strand lead to deletions.MutSβ is present in many eukaryotic organisms, but not in prokaryotes.

View Article: PubMed Central - PubMed

Affiliation: Department of Biology, Emory University, Atlanta, Georgia, United States of America.

ABSTRACT
DNA mismatch repair greatly increases genome fidelity by recognizing and removing replication errors. In order to understand how this fidelity is maintained, it is important to uncover the relative specificities of the different components of mismatch repair. There are two major mispair recognition complexes in eukaryotes that are homologues of bacterial MutS proteins, MutSα and MutSβ, with MutSα recognizing base-base mismatches and small loop mispairs and MutSβ recognizing larger loop mispairs. Upon recognition of a mispair, the MutS complexes then interact with homologues of the bacterial MutL protein. Loops formed on the primer strand during replication lead to insertion mutations, whereas loops on the template strand lead to deletions. We show here in yeast, using oligonucleotide transformation, that MutSα has a strong bias toward repair of insertion loops, while MutSβ has an even stronger bias toward repair of deletion loops. Our results suggest that this bias in repair is due to the different interactions of the MutS complexes with the MutL complexes. Two mutants of MutLα, pms1-G882E and pms1-H888R, repair deletion mispairs but not insertion mispairs. Moreover, we find that a different MutL complex, MutLγ, is extremely important, but not sufficient, for deletion repair in the presence of either MutLα mutation. MutSβ is present in many eukaryotic organisms, but not in prokaryotes. We suggest that the biased repair of deletion mispairs may reflect a critical eukaryotic function of MutSβ in mismatch repair.

Show MeSH
Related in: MedlinePlus