Mismatch repair in Schizosaccharomyces pombe requires the mutL homologous gene pms1: molecular cloning and functional analysis
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Published on: March 18, 2010
1Institute of Medical Radiobiology, University of Zürich, Switzerland. schaer@imr.unizh.ch
Abstract:
Homologues of the bacterial mutS and mutL genes involved in DNA mismatch repair have been found in organisms from bacteria to humans. Here, we describe the structure and function of a newly identified Schizosaccharomyces pombe that encodes a predicted amino acid sequence of 794 residues with a high degree of homology to MutL related proteins. On the basis of its closer relationship to the eukaryotic "PMS" genes than to the "MLH" genes, we have designated the S. pombe homologue pms1. Disruption of the pms1 gene causes a significant increase of spontaneous mutagenesis as documented by reversion rate measurements. Tetrad analyses of crosses homozygous for the pms1 mutation reveal a reduction of spore viability from > 92% to 80% associated with a low proportion (approximately 50%) of meioses producing four viable spores and a significant, allele-dependent increase of the level of post-meiotic segregation of genetic marker allele pairs. The mutant phenotypes are consistent with a general function of pms1 in correction of mismatched base pairs arising as a consequence of DNA polymerase errors during DNA synthesis, or of hybrid DNA formation between homologous but not perfectly complementary DNA strands during meiotic recombination.
Insights
The Schizosaccharomyces pombe pms1 gene is crucial for DNA mismatch repair. Its disruption significantly increases mutagenesis and reduces spore viability, highlighting its role in maintaining genomic stability.
Area of Science:
- Molecular Biology
- Genetics
- Yeast Biology
Background:
- Homologues of bacterial mutS and mutL genes are involved in DNA mismatch repair across diverse organisms.
- Eukaryotic mismatch repair proteins include PMS and MLH gene families.
Purpose of the Study:
- To identify and characterize a novel Schizosaccharomyces pombe homologue of MutL.
- To investigate the function of the identified S. pombe pms1 gene in DNA repair and genome stability.
Main Methods:
- Gene identification and sequence analysis in S. pombe.
- Gene disruption to create pms1 mutants.
- Spontaneous mutagenesis rate measurements using reversion assays.
- Tetrad analysis to assess spore viability and post-meiotic segregation.
Main Results:
- A new S. pombe gene, designated pms1, homologous to eukaryotic PMS genes was identified.
- Disruption of pms1 led to a significant increase in spontaneous mutation rates.
- pms1 mutants exhibited reduced spore viability and increased post-meiotic segregation, indicating a role in meiosis.
Conclusions:
- The S. pombe pms1 gene plays a critical role in DNA mismatch repair.
- pms1 is essential for correcting DNA polymerase errors and resolving mismatches during meiotic recombination.
- These findings underscore the conserved importance of the mismatch repair pathway in maintaining genome integrity.
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