Yeast oligonucleotide transformation: its mechanism and application to analysis of mutations induced by defined DNA lesions.

We have studied mutagenic specificity of an abasic site by the yeast-transformation procedure using an oligonucleotide containing a single furan-type abasic site. The recipient yeast used was deficient in the major AP endonuclease (apn1). Sequence analysis of the transformants suggested that dATP was incorporated most frequently opposite the abasic site, while dGTP seemed to be incorporated opposite the abasic site in the recipient proficient in apn1. To explore the mechanism of this oligonucleotide transformation, we have also analyzed the transformation with phosphorothioate oligonucleotides with mismatched 3'-end. The results are discussed.