Dual requirement in yeast DNA mismatch repair for MLH1 and PMS1, two homologs of the bacterial mutL gene

1994 ◽  
Vol 14 (1) ◽  
pp. 407-415
Author(s):  
T A Prolla ◽  
D M Christie ◽  
R M Liskay
Keyword(s):  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Genetic Recombination ◽  
Sequence Similarity ◽  
Spontaneous Mutation ◽  
Protein Product ◽  
Mlh1 Gene ◽  
Dna Mismatch ◽  
Postmeiotic Segregation ◽  
Simple Sequence

We have identified a new Saccharomyces cerevisiae gene, MLH1 (mutL homolog), that encodes a predicted protein product with sequence similarity to DNA mismatch repair proteins of bacteria (MutL and HexB) and S. cerevisiae yeast (PMS1). Disruption of the MLH1 gene results in elevated spontaneous mutation rates during vegetative growth as measured by forward mutation to canavanine resistance and reversion of the hom3-10 allele. Additionally, the mlh1 delta mutant displays a dramatic increase in the instability of simple sequence repeats, i.e., (GT)n (M. Strand, T. A. Prolla, R. M. Liskay, and T. D. Petes, Nature [London] 365:274-276, 1993). Meiotic studies indicate that disruption of the MLH1 gene in diploid strains causes increased spore lethality, presumably due to the accumulation of recessive lethal mutations, and increased postmeiotic segregation at each of four loci, the latter being indicative of inefficient repair of heteroduplex DNA generated during genetic recombination. mlh1 delta mutants, which should represent the null phenotype, show the same mutator and meiotic phenotypes as isogenic pms1 delta mutants. Interestingly, mutator and meiotic phenotypes of the mlh1 delta pms1 delta double mutant are indistinguishable from those of the mlh1 delta and pms1 delta single mutants. On the basis of our data, we suggest that in contrast to Escherichia coli, there are two MutL/HexB-like proteins in S. cerevisiae and that each is a required component of the same DNA mismatch repair pathway.

scholarly journals Dual requirement in yeast DNA mismatch repair for MLH1 and PMS1, two homologs of the bacterial mutL gene.

1994 ◽  
Vol 14 (1) ◽  
pp. 407-415 ◽  
Author(s):  
T A Prolla ◽  
D M Christie ◽  
R M Liskay
Keyword(s):  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Genetic Recombination ◽  
Sequence Similarity ◽  
Spontaneous Mutation ◽  
Protein Product ◽  
Mlh1 Gene ◽  
Dna Mismatch ◽  
Postmeiotic Segregation ◽  
Simple Sequence

We have identified a new Saccharomyces cerevisiae gene, MLH1 (mutL homolog), that encodes a predicted protein product with sequence similarity to DNA mismatch repair proteins of bacteria (MutL and HexB) and S. cerevisiae yeast (PMS1). Disruption of the MLH1 gene results in elevated spontaneous mutation rates during vegetative growth as measured by forward mutation to canavanine resistance and reversion of the hom3-10 allele. Additionally, the mlh1 delta mutant displays a dramatic increase in the instability of simple sequence repeats, i.e., (GT)n (M. Strand, T. A. Prolla, R. M. Liskay, and T. D. Petes, Nature [London] 365:274-276, 1993). Meiotic studies indicate that disruption of the MLH1 gene in diploid strains causes increased spore lethality, presumably due to the accumulation of recessive lethal mutations, and increased postmeiotic segregation at each of four loci, the latter being indicative of inefficient repair of heteroduplex DNA generated during genetic recombination. mlh1 delta mutants, which should represent the null phenotype, show the same mutator and meiotic phenotypes as isogenic pms1 delta mutants. Interestingly, mutator and meiotic phenotypes of the mlh1 delta pms1 delta double mutant are indistinguishable from those of the mlh1 delta and pms1 delta single mutants. On the basis of our data, we suggest that in contrast to Escherichia coli, there are two MutL/HexB-like proteins in S. cerevisiae and that each is a required component of the same DNA mismatch repair pathway.

scholarly journals Systematic Mutagenesis of the Saccharomyces cerevisiae MLH1 Gene Reveals Distinct Roles for Mlh1p in Meiotic Crossing Over and in Vegetative and Meiotic Mismatch Repair

2003 ◽  
Vol 23 (3) ◽  
pp. 873-886 ◽  
Author(s):  
Juan Lucas Argueso ◽  
Amanda Wraith Kijas ◽  
Sumeet Sarin ◽  
Julie Heck ◽  
Marc Waase ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Ternary Complex ◽  
Genetic Recombination ◽  
Crossing Over ◽  
Wild Type ◽  
Dna Mismatch ◽  
Biochemical Assays ◽  
Postmeiotic Segregation ◽  
New Alleles

ABSTRACT In eukaryotic cells, DNA mismatch repair is initiated by a conserved family of MutS (Msh) and MutL (Mlh) homolog proteins. Mlh1 is unique among Mlh proteins because it is required in mismatch repair and for wild-type levels of crossing over during meiosis. In this study, 60 new alleles of MLH1 were examined for defects in vegetative and meiotic mismatch repair as well as in meiotic crossing over. Four alleles predicted to disrupt the Mlh1p ATPase activity conferred defects in all functions assayed. Three mutations, mlh1-2, -29, and -31, caused defects in mismatch repair during vegetative growth but allowed nearly wild-type levels of meiotic crossing over and spore viability. Surprisingly, these mutants did not accumulate high levels of postmeiotic segregation at the ARG4 recombination hotspot. In biochemical assays, Pms1p failed to copurify with mlh1-2, and two-hybrid studies indicated that this allele did not interact with Pms1p and Mlh3p but maintained wild-type interactions with Exo1p and Sgs1p. mlh1-29 and mlh1-31 did not alter the ability of Mlh1p-Pms1p to form a ternary complex with a mismatch substrate and Msh2p-Msh6p, suggesting that the region mutated in these alleles could be responsible for signaling events that take place after ternary complex formation. These results indicate that mismatches formed during genetic recombination are processed differently than during replication and that, compared to mismatch repair functions, the meiotic crossing-over role of MLH1 appears to be more resistant to mutagenesis, perhaps indicating a structural role for Mlh1p during crossing over.

Testing for Defective DNA Mismatch Repair in Colorectal Carcinoma: A Practical Guide

2005 ◽  
Vol 129 (11) ◽  
pp. 1385-1389
Author(s):  
Lawrence J. Burgart
Keyword(s):  
Colorectal Carcinoma ◽  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Gene Promoter ◽  
Colorectal Carcinomas ◽  
Mlh1 Gene ◽  
Dna Mismatch ◽  
Dna Mismatch Repair Genes ◽  
Testing Algorithms ◽  
Repair Genes

Abstract Context.—Significant bench and clinical data have been generated during the last decade regarding DNA mismatch repair in colorectal carcinoma. Objectives.—To review clinically relevant aspects of defective DNA mismatch repair in colorectal carcinoma and to suggest testing algorithms for identification of these tumors in the sporadic and familial settings. Data Sources.—This article is based on literature review and clinical testing experience of more than 2000 patient samples. Conclusions.—Approximately 15% of colorectal carcinomas arise as a result of defective DNA mismatch repair. Ninety percent of these carcinomas are sporadic, arising as a result of methylation of the MLH1 gene promoter, silencing expression. These sporadic carcinomas have improved stage-specific prognosis and can be identified by demonstrating aberrant loss of expression with an MLH1 immunoperoxidase stain. Familial colorectal carcinomas with defective DNA mismatch repair (Lynch syndrome) are due to a germline defect in one of several DNA mismatch repair genes. The familial carcinomas are best identified with a combination of immunohistochemistry and molecular microsatellite analysis. This testing facilitates subsequent directed genetic testing of the proband and family members.

scholarly journals Inactivation of DNA Mismatch Repair by Increased Expression of Yeast MLH1

2001 ◽  
Vol 21 (3) ◽  
pp. 940-951 ◽  
Author(s):  
Polina V. Shcherbakova ◽  
Mark C. Hall ◽  
Marc S. Lewis ◽  
Samuel E. Bennett ◽  
Karla J. Martin ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Mutation Rate ◽  
Analytical Ultracentrifugation ◽  
Dna Mismatch Repair ◽  
Genome Instability ◽  
Spontaneous Mutation ◽  
Moderate Increase ◽  
Spontaneous Mutation Rate ◽  
Dna Mismatch ◽  
Mutator Effect

ABSTRACT Inactivation of DNA mismatch repair by mutation or by transcriptional silencing of the MLH1 gene results in genome instability and cancer predisposition. We recently found (P. V. Shcherbakova and T. A. Kunkel, Mol. Cell. Biol. 19:3177–3183, 1999) that an elevated spontaneous mutation rate can also result from increased expression of yeast MLH1. Here we investigate the mechanism of this mutator effect. Hybridization of poly(A)+ mRNA to DNA microarrays containing 96.4% of yeast open reading frames revealed that MLH1overexpression did not induce changes in expression of other genes involved in DNA replication or repair. MLH1overexpression strongly enhanced spontaneous mutagenesis in yeast strains with defects in the 3′→5′ exonuclease activity of replicative DNA polymerases δ and ɛ but did not enhance the mutation rate in strains with deletions of MSH2, MLH1, orPMS1. This suggests that overexpression ofMLH1 inactivates mismatch repair of replication errors. Overexpression of the PMS1 gene alone caused a moderate increase in the mutation rate and strongly suppressed the mutator effect caused by MLH1 overexpression. The mutator effect was also reduced by a missense mutation in the MLH1 gene that disrupted Mlh1p-Pms1p interaction. Analytical ultracentrifugation experiments showed that purified Mlh1p forms a homodimer in solution, albeit with a K d of 3.14 μM, 36-fold higher than that for Mlh1p-Pms1p heterodimerization. These observations suggest that the mismatch repair defect in cells overexpressingMLH1 results from an imbalance in the levels of Mlh1p and Pms1p and that this imbalance might lead to formation of nonfunctional mismatch repair complexes containing Mlh1p homodimers.

scholarly journals Mismatch repair genes in Lynch syndrome: a review

2009 ◽  
Vol 127 (1) ◽  
pp. 46-51 ◽  
Author(s):  
Felipe Cavalcanti Carneiro da Silva ◽  
Mev Dominguez Valentin ◽  
Fábio de Oliveira Ferreira ◽  
Dirce Maria Carraro ◽  
Benedito Mauro Rossi
Keyword(s):  
Lynch Syndrome ◽  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Cancer Surveillance ◽  
Mismatch Repair Gene ◽  
Mismatch Repair Genes ◽  
Repair Gene ◽  
Dna Mismatch ◽  
Postmeiotic Segregation ◽  
Repair Genes

Lynch syndrome represents 1-7% of all cases of colorectal cancer and is an autosomal-dominant inherited cancer predisposition syndrome caused by germline mutations in deoxyribonucleic acid (DNA) mismatch repair genes. Since the discovery of the major human genes with DNA mismatch repair function, mutations in five of them have been correlated with susceptibility to Lynch syndrome: mutS homolog 2 (MSH2); mutL homolog 1 (MLH1); mutS homolog 6 (MSH6); postmeiotic segregation increased 2 (PMS2); and postmeiotic segregation increased 1 (PMS1). It has been proposed that one additional mismatch repair gene, mutL homolog 3 (MLH3), also plays a role in Lynch syndrome predisposition, but the clinical significance of mutations in this gene is less clear. According to the InSiGHT database (International Society for Gastrointestinal Hereditary Tumors), approximately 500 different LS-associated mismatch repair gene mutations are known, primarily involving MLH1 (50%) and MSH2 (40%), while others account for 10%. Much progress has been made in understanding the molecular basis of Lynch Syndrome. Molecular characterization will be the most accurate way of defining Lynch syndrome and will provide predictive information of greater accuracy regarding the risks of colon and extracolonic cancer and enable optimal cancer surveillance regimens.

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