A POLY(DA-DT) TRACT IS A COMPONENT OF THE RECOMBINATION INITIATION SITE AT THE ARG4 LOCUS IN SACCHAROMYCES-CEREVISIAE

An initiation site for meiotic gene conversion is located in the promoter region of the ARG4 locus in Saccharomyces cerevisiae. We have tested the hypothesis that the initiation site is identical with the promoter by making a series of small deletions that remove specific promoter elements. Disruption of most promoter elements does not lower the level of gene conversion in ARG4, and analysis of RNA levels at the time of recombination in meiosis reveals no direct correlation between the level of ARG4 transcript and the level of gene conversion in ARG4. However, deletion of a tract of 14 A residues located at the peak of the gene conversion gradient decreases the number of gene conversion events stimulated by the initiation site to 25 to 35% of the normal level. We conclude that the poly(dA . dT) tract is responsible for most but not all the high levels of meiotic gene conversion observed in ARG4.