The strong ADH1 promoter stimulates mitotic and meiotic recombination at the ADE6 gene of Schizosaccharomyces pombe.

The effect of the strong promoter from the alcohol dehydrogenase gene on mitotic and meiotic intragenic recombination has been studied at the ade6 locus of the fission yeast Schizosaccharomyces pombe. A 700-bp fragment containing the functional adh1 promoter was used to replace the weak wild-type promoter of the ade6 gene. Analysis of mRNA showed that strains with this ade6::adh1 fusion construct had strongly elevated ade6-specific mRNA levels during vegetative growth as well as in meiosis. These increased levels of mRNA correlated with a 20- to 25-fold stimulation of intragenic recombination in meiosis and a 7-fold increased prototroph formation during vegetative growth. Analysis of flanking marker configurations of prototrophic recombinants indicated that simple conversions as well as conversions associated with crossing over were stimulated in meiosis. The strongest stimulation of recombination was observed when the adh1 promoter was homozygous. Studies with heterologous promoter configurations revealed that the highly transcribed allele was the preferred acceptor of genetic information. The effect of the recombinational hot spot mutation ade6-M26 was also investigated in this system. Its effect was only partly additive to the elevated recombination rate generated by the ade6::adh1 fusion construct.