Studies on the inhibition by alpha-amanitin of single-step addition reactions and productive RNA synthesis catalysed by wheat-germ RNA polymerase II.
The rate of formation of a single phosphodiester bond with UTP substrate, U-A primer, poly[d(A-T)] template and wheat-germ RNA polymerase II is greatly depressed in the presence of alpha-amanitin. Half-maximal inhibition occurs at 0.04 microgram/ml, in close agreement with published values for inhibition of productive RNA synthesis with class II RNA polymerases from higher-plant species. However, a sizeable proportion of U-A-U synthesis is resistant to inhibition by excess alpha-amanitin. In the additional presence of ATP, i.e. under experimental conditions permitting RNA chain elongation, the synthesis of poly[r(A-U)] is arrested after the formation of the first phosphodiester bond. The results support the contention that the main enzymic process disrupted by alpha-amanitin is the translocation step of the transcription complex along the DNA template.
de Mercoyrol
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Centre de Biochimie et de Biologie Moléculaire, Centre National de la Recherche Scientifique, Marseille, France.
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D000241:Adenosine / Q000378:metabolism; D000546:Amanitins / Q000494:pharmacology*; D000818:Animals; D002384:Catalysis; D010726:Phosphodiesterase Inhibitors / Q000378:metabolism*; D012313:RNA / Q000096:biosynthesis*; D012319:RNA Polymerase II / Q000378:metabolism*; D014908:Triticum; D014498:Uracil / Q000378:metabolism
D000546:Amanitins; D010726:Phosphodiesterase Inhibitors; D014498:Uracil; D012313:RNA; D012319:RNA Polymerase II; D000241:Adenosine