Complex transcriptional and post‐transcriptional regulation of an enzyme for lipopolysaccharide modification

Abstract

Summary The PhoQ/PhoP two-component system activates many genes for lipopolysaccharide (LPS) modification when cells are grown at low Mg2+ concentrations. An additional target of PhoQ and PhoP is MgrR, an Hfq-dependent small RNA that negatively regulates expression of eptB, also encoding a protein that carries out LPS modification. Examination of LPS confirmed that MgrR effectively silences EptB; the phosphoethanolamine modification associated with EptB is found in ΔmgrR::kan but not mgrR+ cells. Sigma E has been reported to positively regulate eptB, although the eptB promoter does not have the expected Sigma E recognition motifs. The effects of Sigma E and deletion of mgrR on levels of eptB mRNA were independent, and the same 5′ end was found in both cases. In vitro transcription and the behavior of transcriptional and translational fusions demonstrate that Sigma E acts directly at the level of transcription initiation for eptB, from the same start point as Sigma 70. The results suggest that when Sigma E is active, synthesis of eptB transcript outstrips MgrR-dependent degradation; presumably the modification of LPS is important under these conditions. Adding to the complexity of eptB regulation is a second sRNA, ArcZ, which also directly and negatively regulates eptB.

A small RNA activates CFA synthase by isoform-specific mRNA stabilization

“…The bacterial envelope acts as both protective barrier and interaction site with the environment. While it has long been known that sRNAs modulate general membrane permeability by targeting the mRNAs of outer membrane porins, more recent studies have also discovered sRNA‐mediated regulations of enzymes that modify the lipopolysaccharides decorating the outside of the envelope (Moon and Gottesman, 2009; Corcoran et al, 2012; Moon et al, 2013). The positive regulation by RydC identified here offers a unique opportunity to understand how RNA‐based regulation is utilized to regulate another important trait of the bacterial envelope, that is, the stability of its membranes.…”

Dual RNA-seq of pathogen and host

“…The resulting lncRNA products might simply represent byproducts of transcription and are typically rapidly degraded after synthesis (Clark et al, 2012). (Albrecht et al, 2010(Albrecht et al, , 2011Chabelskaya et al, 2014;Chao et al, 2012;Gong et al, 2011;Grieshaber et al, 2006;Mann et al, 2012;Moon et al, 2013;Ortega et al, 2012;PadalonBrauch et al, 2008;Pfeiffer et al, 2007) crRNA, (Bhaya et al, 2011;Heidrich and Vogel, 2013;Sampson et al, 2013;van der Oost et al, 2014) (Georg and Hess, 2011;Giangrossi et al, 2010;GonzaloAsensio et al, 2013;Gottesman and Storz, 2011;Lasa et al, 2011;Lee and Groisman, 2010;Padalon-Brauch et al, 2008;Sesto et al, 2013) circRNAs rare varies arise from the 3'-5' ligation of both ends of linear RNA molecules n. a. -- (Doose et al, 2013;Vicens and Cech, 2009) - (Conway et al, 2014;Weinberg et al, 2009) Carpenter et al, 2013;Gomez et al, 2013;Iiott et al, 2014;Imamura et al, 2014;Li et al, 2014;Rapicavoli et al, 2013) poly ( …”

“…Moreover, in vitro studies with Salmonella and pathogenic E. coli suggest various sRNAs that contribute to pathogenicity. These include the Salmonella pathogenicity island 1 (SPI-1)-associated InvR and DapZ sRNAs, the lipopolysaccharide (LPS) synthesis-controlling MgrR (Moon et al, 2013), or the virulence effector-targeting SgrS sRNA (Papenfort et al, 2013). However, inhibition of many of these well characterized sRNA genes by transposon insertions did not lead to a pronounced growth defect in in vivo models of infection (Barquist et al, 2013;Chaudhuri et al, 2013).…”

“…Furthermore, there are currently three confirmed HilD/HilA-responsive sRNAs, InvR , DapZ and IsrJ (Padalon-Brauch et al, 2008), and two PhoPdependent sRNAs, MgrR (Moon et al, 2013) and STnc440 (Y. Chao, personal communication).…”

Kdo2‐lipid A: structural diversity and impact on immunopharmacology

“…They often regulate a subset of specific modification enzymes which are also regulated by the PhoP-PhoQ or PmrA-PmrB systems; their regulation often leads to fine-tuned expression of these enzymes rather than simply switching them ‘on’ or ‘off’. For instance, in E. coli expression of eptB is negatively regulated by sRNAs MgrR which itself is activated by PhoP-PhoQ system and ArcZ whose expression is mediated by the oxygen-sensing ArcA-ArcB two-component systems (Moon et al , 2013). Expression of eptB is also subject to the regulation of Sigma E (σ E ) which is a general regulator of envelope stress caused by unfolded or misfolded proteins in the periplasm (Moon et al , 2013).…”