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Gene conversion associated with site-specific recombination in yeast plasmid pSR1
H Matsuzaki1, H Araki, Y Oshima
1Department of Fermentation Technology, Faculty of Engineering, Osaka University, Japan.
Molecular and Cellular Biology
|February 1, 1988
Summary
Intramolecular recombination in yeast plasmids is frequently catalyzed by a specific gene, independent of the RAD52 gene. This process, occurring at inverted repeats, also drives high-frequency gene conversion, correcting DNA sequence variations.
Area of Science:
- Molecular Biology
- Yeast Genetics
- DNA Recombination
Background:
- The Zygosaccharomyces rouxii plasmid pSR1 contains inverted repeats of 959 base pairs.
- Intramolecular recombination occurs frequently within these repeats in Saccharomyces cerevisiae and Z. rouxii.
Purpose of the Study:
- To investigate the mechanism and genetic control of intramolecular recombination at inverted repeats in yeast.
- To identify the specific DNA sequences and host factors involved in initiating and mediating this recombination process.
Main Methods:
- Construction and analysis of mutant plasmids with linker insertions and deletions within the inverted repeats.
- Assessing recombination frequency and gene conversion in Saccharomyces cerevisiae, including rad52-1 mutant strains.
- Mapping the initiation site for intramolecular recombination.
Main Results:
- A 58-bp region within the inverted repeats, featuring a 14-bp dyad symmetry and a 3-bp spacer, was identified as the recombination initiation site.
- Recombination is catalyzed by a protein encoded by the R gene and is independent of the host RAD52 gene.
- High-frequency gene conversion (3-50%) was observed, correcting sequence heterogeneity within the inverted repeats, even in rad52-1 mutants.
Conclusions:
- The R gene product catalyzes intramolecular recombination at a specific site within inverted repeats, independent of RAD52.
- Gene conversion efficiently homogenizes sequences within the inverted repeats, suggesting a mechanism involving branch migration and DNA replication.