title: RNA type III secretion signals that require Hfq.
abstract: Salmonella virulence is largely mediated by two type III secretion systems (T3SS) that deliver effector proteins from the bacterium to a host cell; however, the secretion signal is poorly defined. Effector N termini are thought to contain the signal, but they lack homology, possess no identifiable motif, and adopt intrinsically disordered structures. Alternative studies suggest that RNA-encoded signals may also be recognized and that they can be located in the 5' untranslated leader sequence. We began our study by establishing the minimum sequence required for reporter translocation. Untranslated leader sequences predicted from 42 different Salmonella effector proteins were fused to the adenylate cyclase reporter (CyaA'), and each of them was tested for protein injection into J774 macrophages. RNA sequences derived from five effectors, gtgA, cigR, gogB, sseL, and steD, were sufficient for CyaA' translocation into host cells. To determine the mechanism of signal recognition, we identified proteins that bound specifically to the gtgA RNA. One of the unique proteins identified was Hfq. Hfq had no effect upon the translocation of full-length CigR and SteD, but injection of intact GtgA, GogB, and SseL was abolished in an hfq mutant, confirming the importance of Hfq. Our results demonstrated that the Salmonella pathogenicity island 2 (SPI-2) T3SS assembled into a functional apparatus independently of Hfq. Since particular effectors required Hfq for translocation, Hfq-RNA complexes may participate in signal recognition.
authors: Department of Microbiology and Immunology, Oregon Health and Science University, Portland, Oregon, USA.
authors: George S
authors: GS
authors: Niemann
authors: Roslyn N
authors: RN
authors: Brown
authors: Ivy T
authors: IT
authors: Mushamiri
authors: Nhu T
authors: NT
authors: Nguyen
authors: Rukayat
authors: R
authors: Taiwo
authors: Afke
authors: A
authors: Stufkens
authors: Richard D
authors: RD
authors: Smith
authors: Joshua N
authors: JN
authors: Adkins
authors: Jason E
authors: JE
authors: McDermott
authors: Fred
authors: F
authors: Heffron
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics / Q000502:physiology; D044404:Genomic Islands / Q000235:genetics*; D009690:Nucleic Acid Conformation; D012329:RNA, Bacterial / Q000737:chemistry / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012486:Salmonella typhimurium / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012329:RNA, Bacterial
references: IUBMB Life. 2000 May;49(5):341-51
references: 10902565
references: J Proteome Res. 2008 Aug;7(8):3354-63
references: 18597511
references: J Bacteriol. 1998 Sep;180(18):4912-21
references: 9733695
references: Science. 1997 Nov 7;278(5340):1140-3
references: 9353199
references: PLoS Pathog. 2009 Feb;5(2):e1000306
references: 19229334
references: Cell Microbiol. 2009 May;11(5):719-29
references: 19215225
references: Infect Immun. 2011 Jan;79(1):33-43
references: 20974834
references: J Struct Biol. 2003 Apr;142(1):133-43
references: 12718925
references: Nature. 2001 Nov 1;414(6859):77-81
references: 11689946
references: Proc Natl Acad Sci U S A. 2007 Feb 27;104(9):3502-7
references: 17360673
references: Gene. 2003 Jul 17;312:151-63
references: 12909351
references: Infect Immun. 2005 Oct;73(10):6260-71
references: 16177297
references: Mol Microbiol. 1999 Feb;31(4):1139-48
references: 10096081
references: Mol Microbiol. 2007 Jan;63(1):193-217
references: 17163975
references: Nature. 2001 Oct 25;413(6858):852-6
references: 11677609
references: J Bacteriol. 1996 Dec;178(24):7227-33
references: 8955406
references: Proc Natl Acad Sci U S A. 1995 Dec 19;92(26):11998-2002
references: 8618831
references: Mol Microbiol. 2004 Jan;51(2):483-95
references: 14756788
references: Bioinformatics. 2008 Aug 15;24(16):i112-8
references: 18689811
references: Curr Opin Microbiol. 2007 Apr;10(2):125-33
references: 17395525
references: Nat Methods. 2012 Jun 28;9(7):676-82
references: 22743772
references: Nat Rev Microbiol. 2011 Aug 15;9(8):578-89
references: 21760622
references: Mol Biosyst. 2010 Dec;6(12):2448-58
references: 20877914
references: J Bacteriol. 2005 Mar;187(5):1559-67
references: 15716426
references: J Biol Chem. 1999 Oct 22;274(43):30501-9
references: 10521431
references: Infect Immun. 1998 Mar;66(3):938-43
references: 9488379
references: Nature. 2006 Nov 30;444(7119):567-73
references: 17136086
references: J Bacteriol. 2002 Jun;184(12):3321-8
references: 12029049
references: Nucleic Acids Res. 2011 Apr;39(8):e53
references: 21300640
references: J Bacteriol. 2010 Jan;192(2):560-7
references: 19897643
references: PLoS Genet. 2008 Aug 22;4(8):e1000163
references: 18725932
references: Nucleic Acids Res. 2009 Jan;37(Database issue):D471-8
references: 18849571
references: Nat Biotechnol. 2005 Apr;23(4):475-81
references: 15806100
references: PLoS One. 2009;4(3):e4809
references: 19277208
references: Mol Microbiol. 1997 May;24(4):757-65
references: 9194703
references: Infect Immun. 2007 Feb;75(2):574-80
references: 17158898
references: Curr Opin Microbiol. 2009 Feb;12(1):117-24
references: 19157959
references: Int J Med Microbiol. 2003 Apr;293(1):107-12
references: 12755371
references: Trends Pharmacol Sci. 2002 Sep;23(9):397-9
references: 12237145