FACTORS AFFECTING INVERTED REPEAT STIMULATION OF RECOMBINATION AND DELETION IN SACCHAROMYCES-CEREVISIAE

Inverted DNA repeats are an at-risk motif for genetic instability that can induce both deletions and recombination in yeast. We investigated the role of the length of inverted repeats and size of the DNA separa ting the repeats for deletion and recombination. Stimulation of both d eletion and recombination was directly related to the size of inverted repeats and inversely related to the size of intervening spacers. A p erfect palindrome, formed by two 1.0-kb URA3-inverted repeats, increas ed intra-and interchromosomal recombination in the adjacent region 2,4 00-fold and 17,000-fold, respectively. The presence of a strong origin of replication in the spacer reduced both rates of deletion and recom bination. These results support a model in which the stimulation of de letion and recombination by inverted repeats is initiated by a seconda ry structure formed between single-stranded DNA of inverted repeats du ring replication.