title: Activation of a vmp pseudogene in Borrelia hermsii: an alternate mechanism of antigenic variation during relapsing fever.
abstract: The relapsing fever agent, Borrelia hermsii, undergoes multiphasic antigenic variation to evade its host's immune response. A frequently observed switch is serotype 7 to 26. Unlike silent vmp genes previously characterized, the transcriptionally silent vmp26 sequence was a pseudogene in lacking a start codon. In serotype 7 the location of the silent vmp26 sequence just downstream of vmp7 on the expression plasmid, as well as on the silent plasmid, was also unique. The demonstration of a predicted circular recombination product in serotype 7 but not serotype 21 populations indicates that the pseudogene was activated by an intramolecular recombination producing a deletion of DNA between 20-nucleotide direct repeats in vmp7 and psi vmp26.
authors.affiliation: Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
authors.forename: B I
authors.initials: BI
authors.lastname: Restrepo
authors.forename: C J
authors.initials: CJ
authors.lastname: Carter
authors.forename: A G
authors.initials: AG
authors.lastname: Barbour
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000940:Antigenic Variation / Q000235:genetics*; D000942:Antigens, Bacterial / Q000235:genetics*; D000954:Antigens, Surface / Q000096:biosynthesis / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins; D001483:Base Sequence; D001898:Borrelia / Q000145:classification / Q000235:genetics* / Q000276:immunology; D005260:Female; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D011544:Pseudogenes; D011995:Recombination, Genetic; D012061:Relapsing Fever / Q000276:immunology / Q000382:microbiology*; D012703:Serotyping
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; C067934:VMP7 protein, Borrelia hermsii; C067935:VMP21 antigen, Borrelia