Formation of a single phosphodiester bond by RNA polymerase B from calf thymus is not inhibited by .alpha.-amanitin

Abstract
The template-directed synthesis of a single phosphodiester bond by highly purified calf thymus RNA polymerase B is not inhibited by high concentrations of .alpha.-amanitin (10-6 M). However, a subsequent internucleotide bond is not synthesized in the presence of .alpha.-amanitin. Translocation of the nascent RNA and RNA polymerase B along the DNA template is probably the enzymatic process inhibited by .alpha.-amanitin. The formation of a single phosphodiester bond by RNA polymerase B results in a stable ternary transcription complex, i.e., between the enzyme, the DNA, and the nascent RNA. Under reaction conditions which normally favor the elongation of RNA, the transcriptional process is arrested at initiation by .alpha.-amanitin. Such ternary initiation complexes were isolated by agarose gel electrophoresis.