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Mutations that increase expression of the rpoS gene and decrease its dependence on hfq function in Salmonella typhimurium.
J Bacteriol. 1997 Feb; 179(3):656-62.JB

Abstract

The RpoS transcription factor (also called sigmaS or sigma38) is required for the expression of a number of stationary-phase and osmotically inducible genes in enteric bacteria. RpoS is also a virulence factor for several pathogenic species, including Salmonella typhimurium. The activity of RpoS is regulated in response to many different signals, at the levels of both synthesis and proteolysis. Previous work with rpoS-lac protein fusions has suggested that translation of rpoS requires hfq function. The product of the hfq gene, host factor I (HF-I), is a ribosome-associated, site-specific RNA-binding protein originally characterized for its role in replication of the RNA bacteriophage Qbeta of Escherichia coli. In this study, the role of HF-I was explored by isolating suppressor mutations that map to the region directly upstream of rpoS. These mutations increase rpoS-lac expression in the absence of HF-I and also confer substantial independence from HF-I. DNA sequence analysis of the mutants suggests a model in which the RNA secondary structure near the ribosome binding site of the rpoS mRNA plays an important role in limiting expression in the wild type. Genetic tests of the model confirm its predictions, at least in part. It seems likely that the mutations analyzed here activate a suppression pathway that bypasses the normal HF-I-dependent route of rpoS expression; however, it is also possible that some of them identify a sequence element with an inhibitory function that is directly counteracted by HF-I.

Authors+Show Affiliations

Department of Microbiology and Immunology, West Virginia University Health Sciences Center, Morgantown 26506, USA.No affiliation info available

Pub Type(s)

Journal Article
Research Support, U.S. Gov't, P.H.S.

Language

eng

PubMed ID

9006017

Citation

Brown, L, and T Elliott. "Mutations That Increase Expression of the rpoS Gene and Decrease Its Dependence On Hfq Function in Salmonella Typhimurium." Journal of Bacteriology, vol. 179, no. 3, 1997, pp. 656-62.
Brown L, Elliott T. Mutations that increase expression of the rpoS gene and decrease its dependence on hfq function in Salmonella typhimurium. J Bacteriol. 1997;179(3):656-62.
Brown, L., & Elliott, T. (1997). Mutations that increase expression of the rpoS gene and decrease its dependence on hfq function in Salmonella typhimurium. Journal of Bacteriology, 179(3), 656-62.
Brown L, Elliott T. Mutations That Increase Expression of the rpoS Gene and Decrease Its Dependence On Hfq Function in Salmonella Typhimurium. J Bacteriol. 1997;179(3):656-62. PubMed PMID: 9006017.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Mutations that increase expression of the rpoS gene and decrease its dependence on hfq function in Salmonella typhimurium. AU - Brown,L, AU - Elliott,T, PY - 1997/2/1/pubmed PY - 1997/2/1/medline PY - 1997/2/1/entrez SP - 656 EP - 62 JF - Journal of bacteriology JO - J Bacteriol VL - 179 IS - 3 N2 - The RpoS transcription factor (also called sigmaS or sigma38) is required for the expression of a number of stationary-phase and osmotically inducible genes in enteric bacteria. RpoS is also a virulence factor for several pathogenic species, including Salmonella typhimurium. The activity of RpoS is regulated in response to many different signals, at the levels of both synthesis and proteolysis. Previous work with rpoS-lac protein fusions has suggested that translation of rpoS requires hfq function. The product of the hfq gene, host factor I (HF-I), is a ribosome-associated, site-specific RNA-binding protein originally characterized for its role in replication of the RNA bacteriophage Qbeta of Escherichia coli. In this study, the role of HF-I was explored by isolating suppressor mutations that map to the region directly upstream of rpoS. These mutations increase rpoS-lac expression in the absence of HF-I and also confer substantial independence from HF-I. DNA sequence analysis of the mutants suggests a model in which the RNA secondary structure near the ribosome binding site of the rpoS mRNA plays an important role in limiting expression in the wild type. Genetic tests of the model confirm its predictions, at least in part. It seems likely that the mutations analyzed here activate a suppression pathway that bypasses the normal HF-I-dependent route of rpoS expression; however, it is also possible that some of them identify a sequence element with an inhibitory function that is directly counteracted by HF-I. SN - 0021-9193 UR - https://www.unboundmedicine.com/medline/citation/9006017/Mutations_that_increase_expression_of_the_rpoS_gene_and_decrease_its_dependence_on_hfq_function_in_Salmonella_typhimurium_ L2 - http://jb.asm.org/cgi/pmidlookup?view=long&pmid=9006017 DB - PRIME DP - Unbound Medicine ER -