Open AccessTranscriptional and Translational Control of the Salmonella fliC Gene
Author(s) -
Phillip D. Aldridge,
Joshua P. Gnerer,
Joyce E. Karlinsey,
Kelly T. Hughes
Publication year - 2006
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.00094-06
Subject(s) - biology , flagellin , operon , untranslated region , five prime untranslated region , primer extension , start codon , gene , genetics , coding region , ribosomal binding site , eukaryotic translation , mutant , microbiology and biotechnology , transcription (linguistics) , translation (biology) , messenger rna , linguistics , philosophy
The flagellin genefliC encodes the major component of the flagellum inSalmonella enterica serovar Typhimurium. This study reports the identification of a signal within the 5′ untranslated region (5′UTR) of thefliC transcript required for the efficient expression and assembly of FliC into the growing flagellar structure. Primer extension mapping determined the transcription start site of thefliC flagellin gene to be 62 bases upstream of the AUG start codon. UsingtetA-fliC operon fusions, we show that the entire 62-base 5′UTR region offliC was required for sufficientfliC mRNA translation to allow normal FliC flagellin assembly, suggesting that translation might be coupled to assembly. To identify sequence that might couplefliC mRNA translation to FliC secretion, the 5′ end of the chromosomalfliC gene was mutagenized by PCR-directed mutagenesis. Single base sequences important forfliC -dependent transcription, translation, and motility were identified by usingfliC-lacZ transcriptional and translational reporter constructs. Transcription-specific mutants identified the −10 and −35 regions of the consensus flagellar class 3 gene promoter. Single base changes defective in translation were located in three regions: the AUG start codon, the presumed ribosomal binding site region, and a region near the very 5′ end of thefliC mRNA that corresponded to a potential stem-loop structure in the 5′UTR. Motility-specific mutants resulted from base substitutions only in thefliC -coding region. The results suggest thatfliC mRNA translation is not coupled to FliC secretion by the flagellar type III secretion system.