A stop codon-dependent internal secondary translation initiation region in Escherichia coli rpoS.
Sigma S (sigmaS) encoded by rpoS is a stationary phase-specific sigma subunit of the Escherichia coli RNA polymerase holoenzyme. In many E. coli strains, rpoS has an amber stop as codon 33 (rpoSAm), resulting in a 32-amino-acid-long peptide. Nevertheless, suppressor-free rpoSAm strains have functional sigmaS. This led us to hypothesize the presence of an intracistronic secondary translational initiation region (STIR) in the E. coli rpoS gene. Here, we demonstrate that the STIR is functional and is controlled by the upstream amber stop codon 33. Removal of the primary translational initiation region did not abolish translation from STIR, ruling out translational coupling. Importantly, the functional STIR conferred survival advantage. Taken together, our results reveal a hitherto unknown physiologically significant post-transcriptional process in E. coli rpoSAm strains.
Department of Medicine (D8-4), University of Miami School of Medicine, 1550 NW 10th Avenue, Fox 431A, FL 33136, USA. spochi@med.miami.edu
Pochi Ramalingam
PR
Subbarayan
Malancha
M
Sarkar
D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D018387:Codon, Initiator / Q000235:genetics; D018388:Codon, Terminator / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism; D029968:Escherichia coli Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D014176:Protein Biosynthesis / Q000235:genetics*; D021122:Protein Subunits; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism; D013489:Suppression, Genetic
D001426:Bacterial Proteins; D018387:Codon, Initiator; D018388:Codon, Terminator; D029968:Escherichia coli Proteins; D021122:Protein Subunits; D012808:Sigma Factor; C069567:sigma factor KatF protein, Bacteria