At non permissive temperature (42°C) the ts47 mutation causes substantial abnormalities in the late phase of the phage intracellular development. In these conditions DNA of the D3112 phage is detected both in a free form and integrated into bacterial chromosome. The transcription kinetics in the ts47 mutant at 42°C was indistinguishable from that typical to other early gene mutants (A, B, and C): specifically, the preservation of the first transcription peak along with low activity of late transcription were observed. Similarly to the C gene, the ts47 mutation-carrying locus is involved in regulating the transcription of the D3112 transposable phage late genes. It is suggested that the mechanism underlying the action of the ts47 mutation differs from that of the C gene product. One of the possible explanations is based on the fact that the product of the ts47 locus affects the activity of cellular RNA polymerase via providing more effective recognition of the phage promoters by the RNA polymerase modified with the phage protein C.