title: Alpha-amanitin-resistant D. melanogaster with an altered RNA polymerase II.
abstract: Following EMS mutagenesis we recovered a mutant of D. melanogaster that grows at concentrations of alpha-amanitin lethal to wild-type. To our knowledge this mutant represents the first example of an amanitin-resistant eucaryotic organism. The amanitin resistance of the mutant (AmaC4) is due to an alteration in its DNA-dependent RNA polymerase II, which is approximately 250 times less sensitive to inhibition by amanitin than the wild-type polymerase II whether tested in nuclei, in partially-fractionated extracts or as a highly purified enzyme. While the wild-type enzyme activity is inhibited 50% by 2.1 x 10(-8) M alpha-amanitin, inhibition of 50% of the AmaC4 RNA polymerase II activity requires a toxin concentration of 5.6 x 10(-6) M. The mutation responsible for the amanitin resistance of AmaC4 is on the X chromosome near the vermillion locus.
mesh_terms: D000546:Amanitins / Q000494:pharmacology*; D000818:Animals; D002874:Chromosome Mapping; D012321:DNA-Directed RNA Polymerases / Q000235:genetics*; D004331:Drosophila melanogaster / Q000187:drug effects / Q000201:enzymology* / Q000235:genetics; D004351:Drug Resistance; D005260:Female; D007814:Larva / Q000201:enzymology; D008297:Male; D009154:Mutation; D012319:RNA Polymerase II / Q000037:antagonists & inhibitors / Q000235:genetics*; D014960:X Chromosome
chemical_list: D000546:Amanitins; D012319:RNA Polymerase II; D012321:DNA-Directed RNA Polymerases