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Activation of a vmp pseudogene in Borrella hermsii : an alternate mechanism of antigenic variation during relapsing fever
Author(s) -
Restrepo B. I.,
Carter C. J.,
Barbour A. G.
Publication year - 1994
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/j.1365-2958.1994.tb00423.x
Subject(s) - pseudogene , biology , plasmid , genetics , serotype , antigenic variation , gene , stop codon , virology , recombination , direct repeat , nucleic acid sequence , base sequence , genome
Summary The relapsing fever agent, Borrella 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 Ψ vmp26.