Abstract

We have constructed new shuttle vectors to facilitate the screening of recombinant plasmids after direct transformation of yeast cells. The vectors are pBluescript-based shuttle vectors in which the lacZ marker has been replaced by an analogous system based on the Saccharomyces cerevisiae URA3 gene. DNA fragments are inserted in a polylinker located after the beginning of the URA3 coding sequence. Transformants are selected either by Trp or Leu prototrophy. Plasmids bearing an insert are selected by growth on 5-fluoro-orotic acid (5-FOA), a uracil analog toxic to cells containing a functional URA3+ gene (thus, this method requires the recipient strain to be ura3-); only cells containing a plasmid with an insert that disrupts the functional continuity of the URA3 gene can grow on medium containing 5-FOA. Using these plasmids, we were able to directly reclone the ACE1 gene from genomic DNA by directly transforming a strain deleted for ACE1. These vectors can be used for a variety of purposes including rapid cloning of genes by complementation or expression of fusion genes driven from the URA3 promoter.