Functional interaction of Escherichia coli RNA polymerase with inorganic polyphosphate

Abstract

Background: RNA polymerase from the stationary growth phase cells of Escherichia coli is tightly associated with an acidic compound(s) and exhibits altered promoter selectivity, with reduced transcriptional activity of the genes highly expressed in the exponentially growing cells. Here we have examined the nature of the RNA polymerase-associated acidic compound(s). Results: RNA polymerase isolated from stationary-phase cells of E. coli was found to be tightly associated with inorganic polyphosphates (poly P), and cannot be dissociated even after chromatography on phosphocellulose or DNA-cellulose columns. Since RNA polymerase-poly P complexes reconstituted in vitro showed similar properties, poly P was not binding covalently. The inhibitory effects of poly P on transcription were examined using two forms of the holoenzyme, one containing σ70, the major σ for transcription of the genes expressed during exponential cell growth and the other containing σ38, the principal σ in the stationary growth phase. At low salt concentrations, poly P inhibited transcription by both Eσ70 and Eσ38 holoenzymes. With an increase in the concentration of potassium glutamate, the poly P inhibition was relieved. At high salt concentrations, the Eσ70 holoenzyme is not able to function, but the Eσ38 holoenzyme is however activated. Conclusions: These results show that poly P may play a role in the promoter selectivity control of RNA polymerase in E. coli which is growing under conditions of high osmolarity and in the stationary growth phase. © Blackwell Science Limited.