Molecular characterization of Borrelia burgdorferi erp promoter/operator elements.
Many Borrelia burgdorferi Erp outer surface proteins have been demonstrated to bind the host complement regulator factor H, which likely contributes to the ability of these organisms to evade the host innate immune system. B. burgdorferi controls Erp protein synthesis throughout the bacterial infectious cycle, producing the proteins during mammalian infections but repressing their synthesis during tick infections. Defining the mechanism by which B. burgdorferi regulates the expression of these virulence determinants will provide important insight into the biological and pathogenic properties of the Lyme disease spirochete. The present study demonstrates that two highly conserved DNA sequences located 5' of erp operons specifically bind bacterial proteins. Analyses with B. burgdorferi of transcriptional fusions between erp promoter/operator DNAs and the gene for green fluorescent protein indicated that the expression of these operons is regulated at the level of transcriptional initiation. These analyses also indicated significant differences in the promoter strengths of various erp operons, which likely accounts for reported variations in expression levels of different Erp proteins. Mutagenesis of promoter-gfp fusions demonstrated that at least one of the proteins which bind erp operator DNA functions as a repressor of transcription.
Babb
Kelly
K
Department of Microbiology, Immunology, and Molecular Genetics, University of Kentucky College of Medicine, MS 415 Chandler Medical Center, Lexington, KY 40536-0298, USA.
McAlister
Jason D
JD
Miller
Jennifer C
JC
Stevenson
Brian
B
D001483:Base Sequence; D001665:Binding Sites; D025065:Borrelia burgdorferi / Q000235:genetics*; D004247:DNA / Q000378:metabolism; D008969:Molecular Sequence Data; D009876:Operon; D011401:Promoter Regions, Genetic
D004247:DNA