Gene Expression in Vitro from Deoxyribonucleic Acid of Bacteriophage T7

The in vitro synthesis of lysozyme and RNA polymerase directed by DNA of bacteriophage T7 starts with different lag periods after addition of the template. The difference in lag period before appearance of enzyme could be attributed to a difference in the time needed for transcription. Assuming that the difference in lag phase is caused by a difference in the distance between the promoter and the corresponding gene, and taking into account the average rates of transcription and translation, the locations of the polymerase gene and the lysozyme gene on the phage genome were estimated. The distance between the promoter and the distal end of the lysozyme gene corresponds to an RNA of the molecular weight 2.2 x 106. The polymerase gene is closer to the promoter. Transcription of T7 DNA by Escherichia coli RNA polymerase in vitro does indeed result in a polycistronic messenger RNA containing the information for synthesis of both RNA polymerase and lysozyme.