An improved method for yeast 2 microns plasmid curing.

SMR1-410, a dominant resistance marker, was cloned into the FLP gene of 2 microns DNA to produce the chimeric YEp vector pWX823B. Selection for SMR1-410 at high concentrations of sulfometuron methyl maintained pWX823 at high copy number and resulted in the rapid and efficient loss of native 2 microns DNA. Using this protocol approximately 15% of the cells monitored showed loss of 2 microns DNA. The curing methodology is more efficient and convenient than previous methods and has the added advantage of being applicable to wild-type prototrophic cells.