title: Effect of template conversion from the B to the Z conformation on RNA polymerase activity.
abstract: Transition from the right-handed B to the left-handed Z conformation of DNA was studied by circular dichroism in parallel with the ability of the DNA to support RNA synthesis with Escherichia coli RNA polymerase. Since the B to Z transition is generally induced by a chemical agent, a definitive demonstration that a change in activity is due to the conformational change, and not to the agent itself or to other factors, requires the clear-cut correlation of template activity and conformation under a variety of conditions that result in conformational change. Such correlation was achieved by following the [Co(NH3)6]3+-induced transition of poly(dG-dC) X poly(dG-dC) and poly(dG-dm5C) X poly(dG-dm5C) and the Mg2+-induced transition of poly(dG-dm5C) X poly(dG-dm5C). In addition, conditions were chosen to minimize possible aggregation. In each of these three systems, the B to Z conformational transition was accompanied by a substantial decrease in transcription activity. While the conversion from B to Z of poly(dG-dm5C) X poly(dG-dm5C) is induced by a 25-fold lower concentration of [Co(NH3)6]3+ than that required for the conversion of unmethylated polymer, in both cases the RNA polymerase activity is decreased at the same cation concentration as that producing the conformational transition. Neither [Co(NH3)6]3+ nor Mg2+ inhibits RNA synthesis with control templates that are not converted to Z under the same conditions, such as poly(dA-dT) X poly(dA-dT) or calf thymus DNA with [Co(NH3)6]3+ or poly(dG-dC) X poly(dG-dC) with Mg2+.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D002942:Circular Dichroism; D003035:Cobalt / Q000494:pharmacology; D004247:DNA / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology; D007700:Kinetics; D009690:Nucleic Acid Conformation; D011089:Polydeoxyribonucleotides / Q000378:metabolism; D013698:Templates, Genetic; D014158:Transcription, Genetic
chemical_list: D011089:Polydeoxyribonucleotides; C030862:cobalt ammonium complex; D003035:Cobalt; D004247:DNA; D012321:DNA-Directed RNA Polymerases