Involvement of mouse Mlh1 in DNA mismatch repair and meiotic crossing over

1996 ◽  
Vol 13 (3) ◽  
pp. 336-342 ◽  
Author(s):  
Sean M. Baker ◽  
Annemieke W. Plug ◽  
Tomas A. Prolla ◽  
C. Eric Bronner ◽  
Allie C. Harris ◽  
...  
Keyword(s):  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Crossing Over ◽  
Dna Mismatch

scholarly journals mlh3 separation of function and endonuclease defective mutants display an unexpected effect on meiotic recombination outcomes

2017 ◽  
Author(s):  
Najla Al-Sweel ◽  
Vandana Raghavan ◽  
Abhishek Dutta ◽  
V. P. Ajith ◽  
Luigi Di Vietro ◽  
...  
Keyword(s):  
Dna Replication ◽  
Mismatch Repair ◽  
Protein Interactions ◽  
Meiotic Recombination ◽  
Meiotic Division ◽  
Dna Mismatch Repair ◽  
Crossing Over ◽  
Baker's Yeast ◽  
Protein Protein Interactions ◽  
Dna Mismatch

AbstractMlh1-Mlh3 is an endonuclease hypothesized to act in meiosis to resolve double Holliday junctions into crossovers. It also plays a minor role in eukaryotic DNA mismatch repair (MMR). To understand how Mlh1-Mlh3 functions in both meiosis and MMR, we analyzed in baker’s yeast 60 new mlh3 alleles. Five alleles specifically disrupted MMR, whereas one (mlh3-32) specifically disrupted meiotic crossing over. Mlh1-mlh3 representatives for each separation of function class were purified and characterized. Both Mlh1-mlh3-32 (MMR+, crossover-) and Mlh1-mlh3-45 (MMR-, crossover+) displayed wild-type endonuclease activities in vitro. Msh2-Msh3, an MSH complex that acts with Mlh1-Mlh3 in MMR, stimulated the endonuclease activity of Mlh1-mlh3-32 but not Mlh1-mlh3-45, suggesting that Mlh1-mlh3-45 is defective in MSH interactions. Whole genome recombination maps were constructed for two mlh3 mutants with opposite separation of function phenotypes, and an endonuclease defective mutant. Unexpectedly, all three showed increases in the number of non-crossover events that were not observed in mlh3Δ. Our observations provide a structure-function map for Mlh3 that reveals the importance of protein-protein interactions in regulating Mlh1-Mlh3’s enzymatic activity. They also illustrate how defective meiotic components can alter the fate of meiotic recombination intermediates, providing new insights for how meiotic recombination pathways are regulated.Author SummaryDuring meiosis, diploid germ cells that become eggs or sperm undergo a single round of DNA replication followed by two consecutive chromosomal divisions. The segregation of chromosomes at the first meiotic division is dependent in most organisms on at least one genetic exchange, or crossover event, between chromosome homologs. Homologs that do not receive a crossover frequently undergo non-disjunction at the first meiotic division, yielding gametes that lack chromosomes or contain additional copies. Such events have been linked to human disease and infertility. Recent studies suggest that the Mlh1-Mlh3 complex is an endonuclease that resolves recombination intermediates into crossovers. Interestingly, this complex also acts as a matchmaker in DNA mismatch repair (MMR) to remove DNA replication errors. How does one complex act in two different processes? We investigated this question by performing a mutational analysis of the baker’s yeast Mlh3 protein. Five mutations were identified that disrupted MMR but not crossing over, and one mutation disrupted crossing over while maintaining MMR. Using a combination of biochemical and genetic analyses to further characterize these mutants we illustrate the importance of protein-protein interactions for Mlh1-Mlh3’s activity. Importantly, we illustrate how defective meiotic components can alter the outcome of meiotic recombination events. They also provide new insights in our understanding of the basis of infertility syndromes.

scholarly journals DNA Mismatch Repair Catalyzed by Extracts of Mitotic, Postmitotic, and Senescent Drosophila Tissues and Involvement of mei-9 Gene Function for Full Activity

1998 ◽  
Vol 18 (3) ◽  
pp. 1436-1443 ◽  
Author(s):  
Arvinder Bhui-Kaur ◽  
Myron F. Goodman ◽  
John Tower
Keyword(s):  
Mismatch Repair ◽  
Dna Mismatch Repair ◽  
Specific Activity ◽  
Excision Repair ◽  
Crossing Over ◽  
Dna Mismatch ◽  
Nucleotide Excision ◽  
Repair Activity ◽  
Development And Aging

ABSTRACT Extracts of Drosophila embryos and adults have been found to catalyze highly efficient DNA mismatch repair, as well as repair of 1- and 5-bp loops. For mispairs T · G and G · G, repair is nick dependent and is specific for the nicked strand of heteroduplex DNA. In contrast, repair of A · A, C · A, G · A, C · T, T · T, and C · C is not nick dependent, suggesting the presence of glycosylase activities. For nick-dependent repair, the specific activity of embryo extracts was similar to that of extracts derived from the entirely postmitotic cells of young and senescent adults. Thus, DNA mismatch repair activity is expressed in Drosophila cells during both development and aging, suggesting that there may be a function or requirement for mismatch repair throughout the Drosophila life span. Nick-dependent repair was reduced in extracts of animals mutant for themei-9 gene. mei-9 has been shown to be required in vivo for certain types of DNA mismatch repair, nucleotide excision repair (NER), and meiotic crossing over and is theDrosophila homolog of the yeast NER gene rad1.

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