Background Glutamyl queuosine-tRNA 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 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. Results 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 β-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. Conclusions 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 .
【저자키워드】 Gene Expression, stringent response, tRNA modification, Osmotic stress,