Induction of sigma factor synthesis in Escherichia coli by the N gene product of bacteriophage lambda.

Thermoinduction of cells of E. coli carrying prophage lambdacI857 within the bfe gene brings about not only "escape synthesis" of core subunits of the DNA-dependent RNA polymerase (RNA nucleotidyltransferase, nucleosidetriphosphate:RNA nucleotidyltransferase, EC 2-7-7-6), but also a striking stimulation of sigma factor synthesis. The latter phenomenon, termed sigma induction, is generally observed after lambda phage infection or prophage induction. A series of experiments with various bacterial and phage strains led us to conclude that the N gene product of lambda is directly involved to the sigma induction. These and other results obtained with mutants defective in transcription termination factor rho suggest the involvement of a rho-sensitive site in the control of sigma gene expression in E. coli.