INSTABILITY OF RTS1 (DRUG-RESISTANT FACTOR) REPLICON - STABILIZATION BY DNA FRAGMENTS DERIVED FROM RTS1

Rts1 is a large naturally occurring plasmid which has a kanamycin resi stance gene and exhibits various temperature-sensitive phenotypes. A s maller derivative of plasmid, pOK, contains the Rts1 replicon and the kanamycin resistance gene of Rts1. This plasmid, pOK, is much more uns table than Rts1 at 42.5 degrees C. A DNA fragment, G(3), 1590 nucleoti des long from Rts1 DNA, stabilized pOK completely at 42.5 degrees C bu t only in the cis configuration. G(3) did not change the copy number o f pOK. The pOK derivative containing G(3) was destabilized by the pres ence of a compatible plasmid containing G(3). G(3) has four inverted r epeats, two 14-base direct repeats, and three ORFs. Smaller fragment o f G(3) also had a stabilization effect and these studies showed that t he ORF does not play any role in stabilization. (C) 1996 Academic Pres s.