On the fidelity of transcription by Escherichia coli ribonucleic acid polymerase

Abstract

The accuracy of transcription has been studied using RNA polymerase from Escherichia coli and synthetic polydeoxynucleotide templates. With the holoenzyme, the highest ratios of non-complementary to complementary bases incorporated into RNA product were observed to be: CTP (1 to 2400), ATP (1 to 9000), UTP (1 to 20,000), GTP (1 to 42,000). The frequency of non-complementary base incorporation into RNA products was not significantly affected by the nature of the template but was found to be primarily determined by the type of non-complementary ribonucleotide. In parallel experiments it was observed that the fidelity of core enzyme was similar to that of holoenzyme. Although removal of sigma factor from holoenzyme had no appreciable effect on non-complementary base-insertion by RNA polymerase, it was observed that the addition of sigma factor to core enzyme stimulated both complementary and non-complementary bases to an equal extent. With poly[d(A-T)]·poly[d(A-T)] as template, nearest-neighbor analysis revealed that CTP was invariably incorporated into the RNA product in juxtaposition with dAMP on the template. Thus, the most frequent error catalyzed by RNA polymerase may be classified as a transition, dA-rU to dA-rC.