Gene conversion associated with site-specific recombination in yeast plasmid pSR1.
A circular DNA plasmid, pSR1, isolated from Zygosaccharomyces rouxii has a pair of inverted repeats consisting of completely homologous 959-base pair (bp) sequences. Intramolecular recombination occurs frequently at the inverted repeats in cells of Saccharomyces cerevisiae, as well as in Z. rouxii, and is catalyzed by a protein encoded by the R gene of its own genome. The recombination is, however, independent of the RAD52 gene of the host genome. A site for initiation of the intramolecular recombination in the S. cerevisiae host was delimited into, at most, a 58-bp region in the inverted repeats by using mutant plasmids created by linker insertion. The 58-bp region contains a pair with 14-bp dyad symmetry separated by a 3-bp spacer sequence. The recombination initiated at this site was accompanied by a high frequency of gene conversion (3 to 50% of the plasmid clones examined). Heterogeneity created by the linker insertion or by a deletion (at most 153 bp so far tested) at any place on the inverted repeats was converted to a homologous combination by the gene conversion, even in the rad52-1 mutant host. A mechanism implying branch migration coupled with DNA replication is discussed.
Matsuzaki
H
H
Department of Fermentation Technology, Faculty of Engineering, Osaka University, Japan.
Araki
H
H
Oshima
Y
Y
D001483:Base Sequence; D003001:Cloning, Molecular; D004926:Escherichia coli / Q000235:genetics; D005785:Gene Conversion; D005800:Genes, Fungal; D008969:Molecular Sequence Data; D009154:Mutation; D010957:Plasmids; D011995:Recombination, Genetic; D012440:Saccharomyces / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics*