The Lyme disease spirochete's BpuR DNA/RNA-binding protein is differentially expressed during the mammal-tick infectious cycle, which affects translation of the SodA superoxide dismutase

When the Lyme disease spirochete, Borrelia burgdorferi, transfers from a feeding tick into a human or other vertebrate host, the bacterium produces vertebrate-specific proteins and represses factors needed for arthropod colonization. Previous studies determined that the B. burgdorferi BpuR protein binds to its own mRNA and autoregulates its translation, and also serves as co-repressor of erp transcription. Here, we demonstrate that B. burgdorferi controls transcription of bpuR, expressing high levels of bpuR during tick colonization but significantly less during mammalian infection. The master regulator of chromosomal replication, DnaA, was found to bind specifically to a DNA sequence that overlaps the bpuR promoter. Cultured B. burgdorferi that were genetically manipulated to produce elevated levels of BpuR exhibited altered levels of several proteins, although BpuR did not impact mRNA levels. Among these was the SodA superoxide dismutase, which is essential for mammalian infection. BpuR bound to sodA mRNA in live B. burgdorferi, and a specific BpuR-binding site was mapped 5 ' of the sodA open reading frame. Recognition of posttranscriptional regulation of protein levels by BpuR adds another layer to our understanding of the B. burgdorferi regulome, and provides further evidence that bacterial protein levels do not always correlate directly with mRNA levels. National Institutes of Heath [R21AI120602, R21AI139956, R03AI113648, P20GM113123]; Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health; High-End Instrumentation Grant [S10RR029127]; Office of the Vice President for Research; Markey Cancer Center; NCI Center Core Support Grant [P30 CA177558] These studies were funded by grants from the National Institutes of Heath: R21AI120602 (to B. Stevenson), R21AI139956 (to B. Stevenson, C.A. Brissette, W.R. Zuckert, and P. Schlax), R03AI113648 (to B. Stevenson, J. Seshu, and J. Livny) and P20GM113123 (to C.A. Brissette); and by the Division of Intramural Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health (to P.E. Stewart, K. Tilly, A. Bestor, and P.A Rosa). The Orbitrap mass spectrometer was acquired by High-End Instrumentation Grant S10RR029127 (to H. Zhu). The University of Kentucky Flow Cytometry & Immune Function core facility is supported in part by the Office of the Vice President for Research, the Markey Cancer Center and an NCI Center Core Support Grant (P30 CA177558) to the University of Kentucky Markey Cancer Center.