Both DNA topoisomerases I and II relax 2 micron plasmid DNA in living yeast cells.
Measurements at various temperatures of the linking number of yeast 2 microns plasmid DNA in wild-type cells and in cells bearing mutations in the DNA topoisomerase I and II genes show that bulk 2 microns plasmid minichromosome are maintained in a relaxed state by the combined action of topoisomerases I and II. Bulk 2 microns minichromosomes are not under torsional stress in vivo and are not substrates for a putative gyrase-like topoisomerase.
D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D004250:DNA Topoisomerases, Type II / Q000378:metabolism*; D004278:DNA, Superhelical; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000235:genetics*
D004278:DNA, Superhelical; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II