Preferential cleavage of plasmid-based R-loops and D-loops by Drosophila topoisomerase IIIbeta.

ABSTRACT: The topoisomerase (topo) III enzymes are found in organisms ranging from bacteria to humans, yet the precise cellular function of these enzymes remains to be determined. We previously found that Drosophila topo IIIbeta can relax plasmid DNA only if the DNA is first hypernegatively supercoiled. To investigate the possibility that topo IIIbeta requires a single-stranded region for its relaxation activity, we formed R-loops and D-loops in plasmids. In addition to containing a single-stranded region, these R-loops and D-loops have the advantage of being covalently closed and supercoiled, thus allowing us to assay for supercoil relaxation. We found that topo IIIbeta preferentially cleaves, rather than relaxes, these substrates. The cleavage of the R-loops and D-loops, which is primarily in the

SUBMITTER: Wilson-Sali T 

PROVIDER: S-EPMC123005 | biostudies-literature | 2002 Jun

REPOSITORIES: biostudies-literature