title: Global systems-level analysis of Hfq and SmpB deletion mutants in Salmonella: implications for virulence and global protein translation.
abstract: Using sample-matched transcriptomics and proteomics measurements it is now possible to begin to understand the impact of post-transcriptional regulatory programs in Enterobacteria. In bacteria post-transcriptional regulation is mediated by relatively few identified RNA-binding protein factors including CsrA, Hfq and SmpB. A mutation in any one of these three genes, csrA, hfq, and smpB, in Salmonella is attenuated for mouse virulence and unable to survive in macrophages. CsrA has a clearly defined specificity based on binding to a specific mRNA sequence to inhibit translation. However, the proteins regulated by Hfq and SmpB are not as clearly defined. Previous work identified proteins regulated by hfq using purification of the RNA-protein complex with direct sequencing of the bound RNAs and found binding to a surprisingly large number of transcripts. In this report we have used global proteomics to directly identify proteins regulated by Hfq or SmpB by comparing protein abundance in the parent and isogenic hfq or smpB mutant. From these same samples we also prepared RNA for microarray analysis to determine if alteration of protein expression was mediated post-transcriptionally. Samples were analyzed from bacteria grown under four different conditions; two laboratory conditions and two that are thought to mimic the intracellular environment. We show that mutants of hfq and smpB directly or indirectly modulate at least 20% and 4% of all possible Salmonella proteins, respectively, with limited correlation between transcription and protein expression. These proteins represent a broad spectrum of Salmonella proteins required for many biological processes including host cell invasion, motility, central metabolism, LPS biosynthesis, two-component regulatory systems, and fatty acid metabolism. Our results represent one of the first global analyses of post-transcriptional regulons in any organism and suggest that regulation at the translational level is widespread and plays an important role in virulence regulation and environmental adaptation for Salmonella.
authors.affiliation: Biological Sciences Division, Pacific Northwest National Laboratory, Richland, Washington, United States of America.
authors.forename: Charles
authors.initials: C
authors.lastname: Ansong
authors.forename: Hyunjin
authors.initials: H
authors.lastname: Yoon
authors.forename: Steffen
authors.initials: S
authors.lastname: Porwollik
authors.forename: Heather
authors.initials: H
authors.lastname: Mottaz-Brewer
authors.forename: Brianne O
authors.initials: BO
authors.lastname: Petritis
authors.forename: Navdeep
authors.initials: N
authors.lastname: Jaitly
authors.forename: Joshua N
authors.initials: JN
authors.lastname: Adkins
authors.forename: Michael
authors.initials: M
authors.lastname: McClelland
authors.forename: Fred
authors.initials: F
authors.lastname: Heffron
authors.forename: Richard D
authors.initials: RD
authors.lastname: Smith
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics* / Q000502:physiology; D005260:Female; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D018390:Gene Targeting; D005798:Genes, Bacterial; D035001:Host Factor 1 Protein / Q000235:genetics* / Q000502:physiology; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D020411:Oligonucleotide Array Sequence Analysis; D009876:Operon; D011409:Propylene Glycols / Q000378:metabolism; D014176:Protein Biosynthesis / Q000235:genetics; D040901:Proteomics / Q000379:methods; D012329:RNA, Bacterial / Q000096:biosynthesis / Q000235:genetics; D012333:RNA, Messenger / Q000096:biosynthesis / Q000235:genetics; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000502:physiology; D012486:Salmonella typhimurium / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism / Q000472:pathogenicity; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D035001:Host Factor 1 Protein; D011409:Propylene Glycols; D012329:RNA, Bacterial; D012333:RNA, Messenger; D016601:RNA-Binding Proteins; C430328:small protein B