Factors Influencing Preferential Utilization of RNA Polymerase Containing Sigma-38 in Stationary-Phase Gene Expression in Escherichia coli

摘要

In order to understand the molecular basis of selective expression of stationary-phase genes by RNA polymerase containing [sigma]~(38) (E[sigma]~(38)) in Escherichia coli, we examined transcription from the stationaryphase promoters, katEP, bolAP, hdeABP, csgBAP, and mcbP, in vivo and in vitro. Although these promoters are preferentially recognized in vivo by E[sigma]~(38), they are transcribed in vitro by both E[sigma]~(38) and E[sigma]~(70) containing the major exponential [sigma], [sigma]~(70). In the presence of high concentrations of glutamate salts, however, only E[sigma]~(38) was able to efficiently transcribe from these promoters, which supports the concept that the promoter selectivity of [sigma]~(38) -containing RNA polymerase is observed only under specific reaction conditions. The examination of 6S RNA, which is encoded by the ssr1 gene in vivo, showed that it reduced E[sigma]~(70) activity during the stationary phase, but this reduction of activity did not result in the elevation of E[sigma]~(38) activity. Thus, the preferential expression of stationary-phase genes by E[sigma]~(38) is unlikely the consequence of selective inhibition of E[sigma]~(70) by 6S RNA.