title: DNA supercoiling in vivo.
abstract: DNA topoisomerase mutants of Escherichia coli and Saccharomyces cerevisiae were used to study the topological state of intracellular DNA. In E. coli, it is shown that switching off the gene topA encoding DNA topoisomerase I leads to an increase in the degree of negative supercoiling of intracellular DNA and inhibition of the growth of the cells: a d(pCpG)16.d(pCpG)16 sequence on a plasmid is also shown to flip from a right-handed B-helical structure to a left-handed Z-helical structure in vivo when topA is switched off. In S. cerevisiae, the topological state of intracellular DNA is little affected by the cellular levels of the topoisomerases.
authors.affiliation: Department of Biochemistry and Molecular Biology, Harvard University, Cambridge, MA 02138.
authors.forename: G N
authors.initials: GN
authors.lastname: Giaever
authors.forename: L
authors.initials: L
authors.lastname: Snyder
authors.forename: J C
authors.initials: JC
authors.lastname: Wang
mesh_terms: D004264:DNA Topoisomerases, Type I / Q000378:metabolism; D004250:DNA Topoisomerases, Type II / Q000378:metabolism; D004269:DNA, Bacterial; D004271:DNA, Fungal; D004278:DNA, Superhelical; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics*; D009154:Mutation; D009690:Nucleic Acid Conformation; D010957:Plasmids; D012441:Saccharomyces cerevisiae / Q000201:enzymology / Q000235:genetics*; D013696:Temperature
chemical_list: D004269:DNA, Bacterial; D004271:DNA, Fungal; D004278:DNA, Superhelical; D004264:DNA Topoisomerases, Type I; D004250:DNA Topoisomerases, Type II