Expression of Shigella flexneri gluQ-rs gene is linked to dksAand controlled by a transcriptional terminator

Glutamyl queuosine-tRNA.sup.Asp synthetase (GluQ-RS) is a paralog of the catalytic domain of glutamyl-tRNA synthetase and catalyzes the formation of glutamyl-queuosine on the wobble position of tRNA.sup.Asp. Here we analyze the transcription of its gene in Shigella flexneri, where it is found downst...

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Bibliographic Details
Published in:BMC microbiology 2012-10, Vol.12 (1), Article 226
Main Authors: Caballero, Valeria C, Toledo, Viviana P, Maturana, Cristian, Fisher, Carolyn R, Payne, Shelley M, Salazar, Juan Carlos
Format: Article
Language:English
Subjects:
Analysis
Gene expression
Genes
Genetic aspects
Genetic transcription
Ligases
Physiological aspects
Shigella flexneri
Transfer RNA
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Summary:Glutamyl queuosine-tRNA.sup.Asp synthetase (GluQ-RS) is a paralog of the catalytic domain of glutamyl-tRNA synthetase and catalyzes the formation of glutamyl-queuosine on the wobble position of tRNA.sup.Asp. Here we analyze the transcription of its gene in Shigella flexneri, where it is found downstream of dksA, which encodes a transcriptional regulator involved in stress responses. The genomic organization, dksA-gluQ-rs, is conserved in more than 40 bacterial species. RT-PCR assays show co-transcription of both genes without a significant change in transcript levels during growth of S. flexneri. However, mRNA levels of the intergenic region changed during growth, increasing at stationary phase, indicating an additional level of control over the expression of gluQ-rs gene. Transcriptional fusions with lacZ as a reporter gene only produced [beta]-galactosidase activity when the constructs included the dksA promoter, indicating that gluQ-rs do not have a separate promoter. Using bioinformatics, we identified a putative transcriptional terminator between dksA and gluQ-rs. Deletion or alteration of the predicted terminator resulted in increased expression of the lacZ reporter compared with cells containing the wild type terminator sequence. Analysis of the phenotype of a gluQ-rs mutant suggested that it may play a role in some stress responses, since growth of the mutant was impaired in the presence of osmolytes. The results presented here, show that the expression of gluQ-rs depends on the dksA promoter, and strongly suggest the presence and the functionality of a transcriptional terminator regulating its expression. Also, the results indicate a link between glutamyl-queuosine synthesis and stress response in Shigella flexneri.
ISSN:1471-2180
1471-2180
DOI:10.1186/1471-2180-12-226