Abstract
A 1.5-kilobase-pair SalI-HindIII (SH) restriction fragment from the region of Saccharomyces cerevisiae chromosome XIV immediately adjacent to the centromere appears to contain sequences that act as a hot spot for mitotic recombination. The presence of SH DNA on an autonomously replicating plasmid stimulates homologous genetic exchange between yeast genomic sequences and those present on the plasmid. In all recombinants characterized, exchange occurs in plasmid yeast sequences adjacent to rather than within the SH DNA. Hybridization analyses reveal that SH-containing plasmids are present in linear as well as circular form in S. cerevisiae and that linear forms are generated by cleavage at specific sites. Presumably, it is the linear form of the plasmid that is responsible for the stimulation of genetic exchange. Based on these observations, it is proposed that this DNA fragment contains a centromere-linked recombination hot spot and that SH-stimulated recombination occurs via a mechanism similar to double-strand-gap repair (J. W. Szostak, T. Orr-Weaver, J. Rothstein, and F. Stahl, Cell 33:25-35 1983).