A rapid and efficient procedure for transformation of Saccharomyces cerevisiae intact cells with plasmid DNA.

A rapid and efficient yeast transformation procedure has been developed through investigation of factors affecting transformation efficiency. The manipulation of the entire procedure can be done within one and one half hours. High yield of transformants is obtained by: adding calf thymus DNA as carrier DNA; adding PEG4000, carrier DNA and plasmid DNA to cell suspension simultaneously; prolonging heat shock at 42 degrees C from 5 min to 25 min and spreading the transformation mixture directly onto agar plates after heat shock. The pretreatment of yeast intact cells with LiAc can be omitted in this procedure. The transformation rates of four types of plasmid DNA were as follows: pCN60: 3.5-7.2 x 10(4) (for linear pCN60/BamHI: 1.6 x 10(5)); YEp13: 1.7-2.6 x 10(4) (for linear YEp13/BamHI: 8.0 x 10(4)); RC4: 3.7 x 10(4); YIp5/StuI: 7.6 x 10(3). Seven recipient strains transformed by using this procedure all reached the yields of over 10(4) transformants per microgramme of DNA.