SEGMENT SELECTION DURING PHASE VARIATION-TYPE REGULATION OF GENE REPLACEMENT MEDIATED BY FLP RECOMBINASE IN THE YEAST SACCHAROMYCES-CEREVISIAE

FLP recombinase has recently been used as a tool to direct the exchang e between invertible DNA segments, called 'Phase variation'-type regul ation of gene replacement in eukaryotic cells. Using an appropriate se lective medium, positive segment selection was shown to be efficient d uring the regulation of gene replacement. The efficiency was determine d from the copy number ratio of invertible segments with the use of th e neomycinphosphotransferase II (NPTII) gene bearing invertible segmen ts located on the episomal yeast plasmid, and the resident 2-mu m circ le. Without the selection the segments copy number ratio was retained in growing cells. The results obtained are an evidence for the efficie ncy of positive segment selection during the 'Phase variation'-type re gulation of gene replacement in eukaryotic cells.