title: Subtelomeric expression regions of Borrelia hermsii linear plasmids are highly polymorphic.
abstract: Borrelia hermsii, a relapsing fever agent, undergoes multiphasic antigenic variation to evade its host's immune response. Serotype specificity is determined by variable membrane lipoproteins, Vmps, which are expressed from genes located near the end of a linear plasmid. Using the polymerase chain reaction and primers representing the promoter of the active vmp and a conserved telomeric sequence, we characterized the subtelomeric expression regions of the 25 known serotypes of strain HS1. The distance from the promoter to the telomere fell into three size classes of approximately 1.0, 1.5, and 2.5 kilobases. In the sequenced serotypes the size differences were accounted for by variable lengths of the vmp genes and intervening sequences between 3' end of the vmp gene and the start of a downstream homology block. The degree of nucleotide identity between different vmp genes, or between the different 3' flanking DNA varied from 39-78%. Thus, there is length and sequence variability not only between vmp genes themselves but also between the 3' flanking regions of vmp genes.
authors: Department of Microbiology, University of Texas Health Science Center, San Antonio 78284-7758.
authors: B I
authors: BI
authors: Restrepo
authors: T
authors: T
authors: Kitten
authors: C J
authors: CJ
authors: Carter
authors: D
authors: D
authors: Infante
authors: A G
authors: AG
authors: Barbour
mesh_terms: D000940:Antigenic Variation / Q000235:genetics*; D000942:Antigens, Bacterial / Q000235:genetics*; D000954:Antigens, Surface / Q000235:genetics*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics*; D001483:Base Sequence; D001898:Borrelia / Q000145:classification / Q000235:genetics* / Q000276:immunology; D005798:Genes, Bacterial; D008074:Lipoproteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011110:Polymorphism, Genetic; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid
chemical_list: D000942:Antigens, Bacterial; D000954:Antigens, Surface; D001425:Bacterial Outer Membrane Proteins; D008074:Lipoproteins; C067934:VMP7 protein, Borrelia hermsii; C067935:VMP21 antigen, Borrelia