TRANSPOGENES - THE TRANSPOSITION-LIKE INTEGRATION OF SHORT SEQUENCE DNA INTO THE YEAST 2-MU PLASMID CREATES THE STB LOCUS AND PLASMID-SIZE POLYMORPHISM

The tyye-2 2 mu plasmid of industrial yeast strains exhibits extensive size polymorphism in the STB (plasmid stability) locus and IR (invert ed repeat)-right region. Comparative DNA sequence analyses of STB alle les identified a 38-bp sequence flanked by a 25-bp direct repeat as th e underlying structural motif. Variable unequal recombination within t he direct repeat accounted for the observed polymorphism of STB allele s. IR-right polymorphism was observed to result from tandem duplicatio n of a 22-bp sequence flanked by a 9-bp direct repeat. The flanking di rect repeats marked both loci as originating from the transposition-li ke integration of short DNA fragments. We call these structures transp ogenes and note that these are hybrid structures of host and foreign D NA which can evolve into functional loci.