Control of gene expression at a bacterial leader RNA, the agn43 gene encoding outer membrane protein Ag43 of Escherichia coli.
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.
Department of Microbiology, University of Pennsylvania, Philadelphia, Pennsylvania, USA.
Anu
A
Wallecha
Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, Ohio, USA.
Heather
H
Oreh
Centre of Immunology and Infection, Hull York Medical School and Department of Biology, University of York, York, United Kingdom.
Marjan W
MW
van der Woude
Center for RNA Molecular Biology, Case Western Reserve University, Cleveland, Ohio, USA Department of Biochemistry, Case Western Reserve University, Cleveland, Ohio, USA pld2@case.edu.
Pieter L
PL
deHaseth
D020121:5' Untranslated Regions / Q000235:genetics*; D018830:Adhesins, Escherichia coli / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics; D048168:Escherichia coli K12 / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D017930:Genes, Reporter; D011401:Promoter Regions, Genetic / Q000235:genetics*; D020871:RNA Stability; D012329:RNA, Bacterial / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D013728:Terminator Regions, Genetic / Q000235:genetics*; D014158:Transcription, Genetic
D020121:5' Untranslated Regions; D018830:Adhesins, Escherichia coli; D001425:Bacterial Outer Membrane Proteins; D012329:RNA, Bacterial; D012333:RNA, Messenger; C118376:antigen 43, E coli