GadX/GadW‐dependent regulation of the Escherichia coli acid fitness island: transcriptional control at the gadY–gadW divergent promoters and identification of four novel 42 bp GadX/GadW‐specific binding sites

Abstract

SummaryEscherichia coli has the remarkable ability to resist severe acid stress for several hours. With the notable exception of the gadBC operon, the most important genes involved in acid resistance are present within the acid fitness island (AFI), a 15 kb H-NS-repressed and RpoS-controlled genome region. The AraC/XylSlike transcriptional regulators GadX and GadW are also encoded within this region. In this article, we show that gadW transcription occurs from two native promoters, which are affected by the transcription of the divergently transcribed and GadX-dependent gadY small RNA, and from the gadX promoter. The gadXW dicistronic transcript is subjected to posttranscriptional processing in which GadY is involved. In contrast, gadW transcription negatively affects gadY transcription. By aligning the GadX/GadW binding site on the gadY promoter with the GadX/ GadW binding sites previously identified in the gadA and gadBC 5Ј regulatory regions, we generated a 42 bp GadX/GadW consensus sequence. DNase I footprinting analyses confirmed that a 42 bp GadX/ GadW binding site, which matched the consensus sequence 5Ј-WANDNCTDWTWKTRAYATWAWMATG KCTGATNTTTWYNTYAK-3Ј, is also present in the regulatory region of the slp-yhiF, hdeAB and gadEmtdEF operons, all of which belong to the AFI. The presence of five GadX/GadW-specific binding sites in the AFI suggests that GadX and GadW may act as H-NS counter-silencers.

Compensations for Diminished Terminal Oxidase Activity in Escherichia coli

“…3). The up-regulation of slp and hdeAB genes, previously shown to be under the concerted control of GadX, GadW, and H-NS (48,49), confirms the involvement of these transcriptional regulators in cydB cells. Furthermore, the adiA gene encoding the arginine-dependent acid resistance system (36) is up-regulated (Figs.…”

Interplay between tolerance mechanisms to copper and acid stress inEscherichia coli

“…Meanwhile, the putative role of CpxR in ybaST transcription has not been experimentally tested (37). In contrast, regulation of ybaST by GadX and GadW is well established, and this occurs in a RpoSdependent manner (38)(39)(40). Notably, RpoS and CpxR also contribute to the cellular adaptation to excess Cu (41,42).…”

cis-Antisense RNA, Another Level of Gene Regulation in Bacteria

“…3A). Processed gadX and gadW mRNAs alone have an enhanced stability (65,97). The processing machinery has been investigated in more detail.…”

“…Previously, other mechanisms of asRNA function such as transcription termination (28,89) or transcript stabilization (66,90,97) were investigated only qualitatively. Because the transcription termination mechanism is not dependent on codegradation, this kind of regulation of the catalytic activity of the asRNA is possible if the asRNA dissociates from its target after action.…”