Retrovirus-like vectors for Saccharomyces cerevisiae: integration of foreign genes controlled by efficient promoters into yeast chromosomal DNA

Abstract Using modified Saccharomyces cerevisiae Ty1 elements located on a 2μ. plasmid, reverse-transcriptase-mediated transposition into yeast chromosomes of expression cassettes containing a foreign gene can be induced. These expression cassettes consist of the yeast ARG 3 and CUP 1 promoter sequences fused to the Escherichia coli galK structural gene. Expression cassettes as large as 2 kb can be inserted into Ty elements and transposed efficiently to various sites in the yeast genome. A third yeast promoter (from the yeast CAR 1 gene) seems to be unsuitable for use in the expression cassette. This may be because it does not allow the transcription run-through necessary for Ty1 transposition. Ways of improving this vector system are discussed, as are its advantages over episomal vector systems.