PHASE VARIATION-TYPE REGULATION OF GENE-EXPRESSION AND GENE REPLACEMENT MEDIATED BY FLP RECOMBINASE IN THE YEAST SACCHAROMYCES-CEREVISIAE

Expression of a neomycin phosphotransferase II (NPTII) gene has been d esigned to be regulated by an FLP-mediated switching of the orientatio n of the NPTII coding region located on the invertible DNA segment in episomal yeast plasmids. Inversion of the segment from inverted to dir ect orientation with respect to the promoter resulted in a dramatic in crease in G418 resistance. FLP also promoted a double reciprocal excha nge between the transforming and the resident 2-mum plasmid, leading t o insertion of the FLP and REP2 genes into the transforming plasmid. T he results demonstrate a possible use of FLP recombinase for 'phase va riation'-type regulation of gene expression and gene replacement in eu karyotic cells.