Control of Gene Expression at a Bacterial Leader RNA, the agn43 Gene Encoding Outer Membrane Protein Ag43 of Escherichia coli

Abstract

The family of agn alleles in Escherichia coli pathovars encodes autotransporters that have been implicated in biofilm formation, autoaggregation, and attachment to cells. The alleles all have long leader RNAs preceding the Ag43 translation initiation codon. Here we present an analysis of the agn43 leader RNA from E. coli K-12. We demonstrate the presence of a rho-independent transcription terminator just 28 bp upstream of the main translation start codon and show that it is functional in vitro. Our data indicate that an as-yet-unknown mechanism of antitermination of transcription must be operative in earlier phases of growth. However, as bacterial cell cultures mature, progressively fewer transcripts are able to bypass this terminator. In the K-12 leader sequence, two in-frame translation initiation codons have been identified, one upstream and the other downstream of the transcription terminator. For optimal agn43 expression, both codons need to be present. Translation from the upstream start codon leads to increased downstream agn43 expression. Our findings have revealed two novel modes of regulation of agn43 expression in the leader RNA in addition to the previously well-characterized regulation of phase variation at the agn43 promoter.

Landscape of RNA polyadenylation inE. coli

“…Its expression is controlled by antitermination of the upstream IsrC RNA (46). However, the stabilized flu mRNA did not contain IsrC, indicating that isrC-flu transcript had been processed and the leader region degraded.…”

Virulence factors, prevalence and potential transmission of extraintestinal pathogenic Escherichia coli isolated from different sources: recent reports

“…The biofilm-forming ability of E. coli is affected by the expression of gene encoding antigenic Agn43 (i.e. flu ), which is involved in aggregation of E. coli cells [64]. Urinary tract infections can often cause bacteremia, especially in hospitalized patients, when, due to catheter contamination, biofilm is produced by invasive ExPEC strains possessing many virulence factors [65–67].…”

Inactivation of Transcriptional Regulators during Within-Household Evolution of Escherichia coli

“…As expected from the PAI duplication in JJ1886, the corresponding mRNA reads were on average twice as abundant in JJ1886 as in JJ1887 (notably excluding the ang43 leader RNA, which is known to regulate Ag43 adhesin expression [34]). Beside these PAIassociated genes, genes with higher expression in JJ1886 than in JJ1887 included those within the lac operon, within three different operons encoding flagella (flhCD, flgBC-DEFG, and fliC), and within a large locus corresponding to the lambdoid mEp460-like prophage ( Fig.…”