title: Polynucleotide phosphorylase negatively controls spv virulence gene expression in Salmonella enterica.
abstract: Mutational inactivation of the cold-shock-associated exoribonuclease polynucleotide phosphorylase (PNPase; encoded by the pnp gene) in Salmonella enterica serovar Typhimurium was previously shown to enable the bacteria to cause chronic infection and to affect the bacterial replication in BALB/c mice (M. O. Clements et al., Proc. Natl. Acad. Sci. USA 99:8784-8789, 2002). Here, we report that PNPase deficiency results in increased expression of Salmonella plasmid virulence (spv) genes under in vitro growth conditions that allow induction of spv expression. Furthermore, whole-genome microarray-based transcriptome analyses of bacteria growing inside murine macrophage-like J774.A.1 cells revealed six genes as being significantly up-regulated in the PNPase-deficient background, which included spvABC, rtcB, entC, and STM2236. Mutational inactivation of the spvR regulator diminished the increased expression of spv observed in the pnp mutant background, implying that PNPase acts upstream of or at the level of SpvR. Finally, competition experiments revealed that the growth advantage of the pnp mutant in BALB/c mice was dependent on spvR as well. Combined, our results support the idea that in S. enterica PNPase, apart from being a regulator of the cold shock response, also functions in tuning the expression of virulence genes and bacterial fitness during infection.
authors.affiliation: Microbiology and Tumor Biology Center, Karolinska Institute, Nobels väg 16, 171 77 Stockholm, Sweden.
authors.forename: Sofia Eriksson
authors.initials: SE
authors.lastname: Ygberg
authors.forename: Mark O
authors.initials: MO
authors.lastname: Clements
authors.forename: Anne
authors.initials: A
authors.lastname: Rytkönen
authors.forename: Arthur
authors.initials: A
authors.lastname: Thompson
authors.forename: David W
authors.initials: DW
authors.lastname: Holden
authors.forename: Jay C D
authors.initials: JC
authors.lastname: Hinton
authors.forename: Mikael
authors.initials: M
authors.lastname: Rhen
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D005260:Female; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D008807:Mice, Inbred BALB C; D009154:Mutation; D020411:Oligonucleotide Array Sequence Analysis; D010957:Plasmids; D011117:Polyribonucleotide Nucleotidyltransferase / Q000235:genetics / Q000378:metabolism*; D020543:Proteome; D012486:Salmonella typhimurium / Q000235:genetics / Q000254:growth & development / Q000472:pathogenicity*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014774:Virulence / Q000235:genetics; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D020543:Proteome; D014157:Transcription Factors; D037521:Virulence Factors; C061928:mkaC protein, Salmonella typhimurium; D011117:Polyribonucleotide Nucleotidyltransferase