[Determination of the direction of the transcription of bacteriophage T4 genes by heat induction of the transcription from recombinant plasmid Pl-promoter: 2 directions in the region of genes 25-29].

The bacterial strains with recombinant plasmids constructed on the basis of vector plasmid pSCC31 and containing BglII fragment of bacteriophage T4 DNA with genes 25-29 have been used in this study. Restriction analysis and subcloning demonstrated that in the case of the recombinant plasmid pRL705, the phage DNA fragment had right orientation for phage late genes transcription, while the opposite one in the plasmid pRL707. Heat induction of plasmids transcription under control of pL promoter led to the substantial change in phage burst size and the production of recombinants, as shown in complementation experiments, the changes in the burst size being dependent both on the host strain and the amber mutant used. On the basis of these data, the conclusion has been drawn that the genes 26 and 25, in contrast to genes 51, 27, 28 and 29, are being transcribed in the counter-clockwise direction on the genomic map, i.e. in the direction of transcription of T4 early genes.