Transformation of Saccharomyces cerevisiae by the lithium acetate/single-stranded carrier DNA/polyethylene glycol protocol

Abstract

▼Transformation of bacteria was first suggested by Griffiths in 1928. It was not until fifty years later that a system was reported by Hinnen et al. (Ref. 1) and Beggs (Ref. 2) for the induction of transformation in Saccharomyces cerevisiae. Further development by Ito et al. (Ref. 3) allowed transformation of intact yeast cells following exposure to alkali cations. This procedure was less complicated, but it yielded only 400 transformants/μg of plasmid DNA. Schiestl and Gietz (Ref. 4) increased the efficiency of the alkali cation protocol to 100 000 transformants/μg plasmid DNA by using single-stranded carrier DNA in the transformation mixture. Since this time, we have streamlined and optimized this protocol to give yields as high as 2.2 × 107 transformants/μg DNA (Ref. 5, 6, 7, 8). High efficiency is essential for transformation of cDNA expression libraries for the two-hybrid system (Ref. 9, 10) as well as other similar systems (Ref. 11, 12, 13). Three transformation protocols are listed here. The ‘standard high-efficiency’ version of the lithium acetate (LiAc)/ single-stranded DNA (ss-DNA)/ polyethylene glycol (PEG) protocol is used when a large number of transformants are required. The ‘large-scale high efficiency’ version is used to obtain the millions of transformants needed to screen complex cDNA libraries. The ‘quick and easy’ version can be used when large numbers of transformants are not required.