Transcription units in bacteriophage T4.

We have investigated the possibility of assigning genes of T4 bacteriophage to their units of transcription (scriptons) by studying gene expression from UV-irradiated DNA templates. Since RNA chains are prematurely terminated on UV-irradiated DNA templates and since the promotor distal part of the RNA chain is deleted, the expression of any gene is inversely proportional to the distance between the promotor and the promotor distal end of the gene. We find that the early genes, 43, 45 and rIIB, are promotor proximal. Since at least genes 43 and rIIB are classified as delayed early genes, these results suggest that their synthesis may require the recognition of new promotors. Additional early genes (44, 62, 42, 46, 47, 55, and rIIA) and some late genes (34, 37, and 38) have also been assigned positions relative to their promotors.