Plasmid multimerization is dependent on RAD52 activity in Saccharomyces cerevisiae.

A mutant plasmid, pX, derived from the 1453 base pair small plasmid, YARp1 (or TRP1 RI circle), consists of 849 base pairs of DNA bearing the TRP1 gene and the ARS1 sequence of Saccharomyces cerevisiae and, unlike YARp1 and other commonly used yeast plasmids, highly multimerizes in a S. cerevisiae host. The multimerization of pX was dependent on RAD52, which is known to be necessary for homologous recombination in S. cerevisiae. Based upon this observation, a regulated system of multimerization of pX with GAL1 promoter-driven RAD52 has been developed. We conclude that the regulated multimerization of pX could provide a useful model system to study genetic recombination in the eukaryotic cell, in particular to investigate recombination intermediates and the effects of various trans-acting mutations on the multimerization and recombination of plasmids.