Regulated Control of the Assembly and Diversity of LPS by Noncoding sRNAs

Figure 3

Hierarchical regulation of glucosoamine-6-phosphate synthase GlmS. (a) Genes glmUS constitute a bicistronic operon, which is cleaved by RNase E at the UGA stop codon of glmU, generating into monocistronic mRNAs that are rapidly degraded. (b) Under GlcN6P limiting conditions, the glmS mRNA base-pairs with intact GlmZ leading to stabilization of the glmS mRNA and also activation of its translation by disrupting inhibitory stem-loop structure that otherwise sequesters the Shine-Dalgarno (SD). This base pairing requires Hfq. Under GlcN6P limiting conditions, GlmZ processing is prevented by sequestration of the RapZ adaptor protein, preventing RapZ targeting to RNase E-mediated degradation of GlmZ. (c) When GlcN6P amounts are high, GlmY sRNA is present in low amounts. This allows the recruitment of RapZ to GlmZ leading to RNase E-mediated cleavage. This cleavage leads to the generation of a processed form of glmZ that lacks complementarity to glmS and hence inability to activate glmS translation due to inability to access SD. This also leads to a rapid degradation of the glmS mRNA.