Construction of a new Escherichia coli-Saccharomyces cerevisiae shuttle plasmid cloning vector allowing positive selection for cloned fragments.

A new E. coli-S. cerevisiae shuttle plasmid cloning vector (pPW263) with a positive type of selection, was constructed. The selection system, based on the regulatory region of lambda phage controlling the expression of tetracycline resistance, was derived from the cloning vector pUN121 (Nilsson et al. 1983). There are three cloning sites in the cI gene, EcoRI, HindIII and BglII, and, in addition, two unique sites in the neighborhood, BamHI and SalI. The size of the vector is 7.8 kb. The maintenance of the vector and the selection in yeast was ensured by the replication region of the 2 mu plasmid and by the URA3 marker gene, respectively.