REP3-derived yeast shuttle vector.

A yeast-shuttle vector using a XbaI-PstI fragment of the 2 microns DNA 1293 bp in length has been constructed. This sequence spans the REP 3 locus and the origin of replication. Besides the 2 microns DNA derived sequences the resulting yeast shuttle vector contains the yeast LEU 2 gene and the Tet' gene of pBR 322. The results demonstrate that the XbaI-PstI fragment is sufficient for proper amplification and partitioning of 2 microns DNA derived yeast-shuttle vectors in yeast. The interruption of the FRT site in this type of vector seems to prevent any recombination between endogenous 2 microns DNA and hybrid plasmid molecules. Moreover, the disturbance of the FLP-system has no influence on the copy number of the plasmid stability.