Cc. Sze et V. Shingler, The alarmone (p)ppGpp mediates physiological-responsive control at the sigma(54)-dependent Po promoter, MOL MICROB, 31(4), 1999, pp. 1217-1228
Transcription from the Pseudomonas-derived sigma(54)- dependent Po promoter
of the dmp operon is mediated by the aromatic-responsive regulator DmpR. H
owever, physiological control is superimposed on this regulatory system cau
sing silencing of the DmpR-mediated transcriptional response in rich media
until the transition between exponential and stationary phase is reached. H
ere, the positive role of the nutritional alarmone (p)ppGpp in DmpR regulat
ion of the Po promoter has been identified and investigated in vivo, Overpr
oduction of (p)ppGpp in a Pseudomonas reporter system was found to allow an
immediate transcriptional response under normally non-permissive condition
s. Conversely (p)ppGpp-deficient Escherichia coil strains were found to be
severely defective in DmpR-mediated transcription, demonstrating the requir
ement for this metabolic signal, A subset of mutations in the beta, beta' a
nd om subunits of RNA polymerase, which confer prototrophy on ppGpp(0) E. c
oil, was also found to restore specific DmpR-mediated transcription from Po
, suggesting that the metabolic signal is mediated directly through the sig
ma(54)-RNA polymerase. These data provide a direct mechanistic link between
the physiological status of the cell and expression from sigma(54) promote
rs.