In vitro transcription of E. coli tRNA genes

Transcription of tRNA genes carried by transducing bacteriophages phi80psu3+ (tRNA1Tyr) and lambdah80T (tRNA2Tyr, tRNA2Glysu36+, tRNA3Thr) was studied in vitro in a system consisting of whole bacteriophage DNA and purified RNA polymerase. In contrast to unusual requirements for tRNA1Tyr gene transcription from DNA fragments, the transcription on whole bacteriophage DNA was found to be relatively not salt sensitive, did not require glycerol and rifampicin-resistant complexes with RNA polymerase were formed in the absence of nucleoside triphosphates. Termination factor rho stimulated the transcription of the tRNA genes as well as that of 4S RNA on lambdah80T DNA template. The stimulatory effect of rho was abolished by rifampicin and seems to be due to the release of RNA polymerase and reinitiation of transcription.