Stability of RNA chain elongation complexes formed with RNA polymerase and denatured DNA templates

A random transcription system was used to analyze RNA chain-elongation complexes with RNA polymerases I and II from mouse ascites sarcoma cells. The molecular size of synthesized RNA was analyzed to characterize the elongation reaction by RNA polymerases. The RNA chain-elongation complex after initiation of RNA synthesis on denatured DNA by RNA polymerase II was not decomposed with heparin which dissociated the DNA-RNA polymerase complex, whereas the elongation complex on denatured DNA by RNA polymerase I was more susceptible to decomposition with heparin. RNA transcribed by RNA polymerase I on denatured DNA 30 min after the start of the reaction contained large RNA around 28S and small RNA. The small RNA could be formed by reinitiation and early termination of elongation. RNA transcribed by RNA polymerase II on denatured DNA was only large RNA around 28S. The elongation reaction by RNA polymerases I and II on denatured DNA was not inhibited by rifamycin AF/013, an inhibitor of initiation. These results suggest that RNA polymerase II could synthesize large transcripts without reinitiation and early termination of elongation and that RNA polymerase II formed more a stable elongation complex on denatured DNA than RNA polymerase I.