Transfer RNA synthesis in vitro.

During infection of Escherichia coli, bacteriophage T4 directs the synthesis of at least eight transfer RNAs and of two stable RNA species of low molecular weight, of unknown function. When T4 DNA is incubated with purified RNA polymerase and the appropriate substrates, a high molecular weight RNA is produced. This RNA, on further incubation with a supernatant fraction prepared from E. coli, is cleaved to several species of RNA. These cleaved RNAs were analyzed by gel electrophoresis and fingerprint techniques, and were found to be similar or identical to those made in vivo. The fingerprint analysis of one of these, a tRNA(Gly), is presented. The molecule made in vitro, except for the absence of modified bases, appears to be identical to the RNA made by T4-infected cells. Therefore, in this system the tRNA genes are transcribed with fidelity, the transcript is cleaved correctly, and the tRNAs are made in good yield.