title: HrpA, an RNA helicase involved in RNA processing, is required for mouse infectivity and tick transmission of the Lyme disease spirochete.
abstract: The Lyme disease spirochete Borrelia burgdorferi must differentially express genes and proteins in order to survive in and transit between its tick vector and vertebrate reservoir. The putative DEAH-box RNA helicase, HrpA, has been recently identified as an addition to the spirochete's global regulatory machinery; using proteomic methods, we demonstrated that HrpA modulates the expression of at least 180 proteins. Although most bacteria encode an HrpA helicase, RNA helicase activity has never been demonstrated for HrpAs and the literature contains little information on the contribution of this protein to bacterial physiology or pathogenicity. In this work, we report that B. burgdorferi HrpA has RNA-stimulated ATPase activity and RNA helicase activity and that this enzyme is essential for both mammalian infectivity by syringe inoculation and tick transmission. Reduced infectivity of strains carrying mutations in the ATPase and RNA binding motif mutants suggests that full virulence expression requires both ATPase and coupled helicase activity. Microarray profiling revealed changes in RNA levels of two-fold, or less in an hrpA mutant versus wild-type, suggesting that the enzyme functions largely or exclusively at the post-transcriptional level. In this regard, northern blot analysis of selected gene products highly regulated by HrpA (bb0603 [p66], bba74, bb0241 [glpK], bb0242 and bb0243 [glpA]) suggests a role for HrpA in the processing and translation of transcripts. In addition to being the first demonstration of RNA helicase activity for a bacterial HrpA, our data indicate that the post-transcriptional regulatory functions of this enzyme are essential for maintenance of the Lyme disease spirochete's enzootic cycle.
authors.affiliation: Department of Biochemistry & Molecular Biology and Department of Microbiology, Immunology & Infectious Diseases, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Aydan
authors.initials: A
authors.lastname: Salman-Dilgimen
authors.affiliation: Department of Biochemistry & Molecular Biology and Department of Microbiology, Immunology & Infectious Diseases, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Pierre-Olivier
authors.initials: PO
authors.lastname: Hardy
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Pediatrics, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Molecular Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Genetics & Developmental Biology, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Immunology, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Justin D
authors.initials: JD
authors.lastname: Radolf
authors.affiliation: Department of Medicine, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Pediatrics, University of Connecticut Health Center, Farmington, Connecticut, United States of America ; Department of Molecular Microbial and Structural Biology, University of Connecticut Health Center, Farmington, Connecticut, United States of America.
authors.forename: Melissa J
authors.initials: MJ
authors.lastname: Caimano
authors.affiliation: Department of Biochemistry & Molecular Biology and Department of Microbiology, Immunology & Infectious Diseases, Snyder Institute for Chronic Diseases, University of Calgary, Calgary, Alberta, Canada.
authors.forename: George
authors.initials: G
authors.lastname: Chaconas
mesh_terms: D000818:Animals; D001426:Bacterial Proteins / Q000502:physiology; D025065:Borrelia burgdorferi / Q000235:genetics* / Q000472:pathogenicity*; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D018884:Ixodes / Q000382:microbiology*; D008193:Lyme Disease / Q000235:genetics / Q000382:microbiology* / Q000635:transmission*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D030781:Organisms, Genetically Modified; D020365:RNA Helicases / Q000502:physiology*; D012323:RNA Processing, Post-Transcriptional / Q000235:genetics*; D014774:Virulence / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D020365:RNA Helicases