Fidelity of in vitro transcription of T3 deoxyribonucleic acid by bacteriophage T3-induced ribonucleic acid polymerase and by Escherichia coli ribonucleic acid polymerase.

The fidelity of in vitro transcription of bacteriophage T3 DNA by T3 RNA polymerase and Escherichia coZi RNA POlymerase have been studied by DNA-RNA hybridizationcompetition studies with regard to (a) asymmetry of transcription and (b) the region of the T3 DNA transcribed by either polymerase. RNA transcribed by T3 RNA polymerase hybridized exclusively with the H strand of T3 DNA-the only strand that is copied in vivo at all times following T3 phage infection. In contrast, RNA transcribed by E. coli RNA polymerase hybridized with both the H and the L strands of 13 DNA, although a high proportion of RNA chains ( > 707,) hybridized with the H strand. Approximately 15 to 20yE of RNA chains hybridized with the L strand, the strand that does not appear to be copied in vivo. The ratio of H to L strand copying by E. coli polymerase was unaltered by the presence of either excess g or p factor or by changes in the ratio of polymerase to DNA in the reaction mixture. Competition-hybridization studies between RNA synthesized in vitro and RNA isolated after T3 phage infection indicate that RNA transcribed in vitro by T3 RNA polymerase contained aJl of the sequences present in late in vivo RNA. In addition, all sequences present in early in vivo RNA were also present in in vitro T3 RNA polymerase products. Thus, in vitro, T3 RNA polymerase transcribed the entire early and late regions of the T3 genome. RNA transcribed by E. coZi RNA polymerase contained all sequences present in early in vivo RNA. In addition, such in vitro RNA also contained nearly 50% of the sequences present in late in viuo RNA. In contrast, RNA transcribed by E. coli RNA polymerase in the presence of termination