The Role of RNase Y in rpoS Transcript Processing in Borrelia burgdorferi

Borrelia burgdorferi is the bacterial agent that causes Lyme disease. The pathogenic bacteria are transmitted to vertebrates through tick feeding and are maintained in nature in an enzootic cycle. The expression of outer surface protein OspC is essential for B. burgdorferi to move from the tick to a mammal. Alternative sigma factor RpoS is responsible for inducing gene (ospC) expression for OspC production during the enzootic cycle. Two versions of rpoS transcripts are observed in vivo: a long one, which is hypothesized to be required for transmission from the tick, and a short one, which is thought to be involved in infection of the mammal. The goal of this project is to understand the mechanism of how the long rpoS transcript is processed so that RpoS protein can activate ospC expression during transmission. We hypothesize that the long rpoS transcript is cleaved by ribonuclease (RNase) Y at the 5′ end. Two specific aims were conducted during the research project: (1) In vitro cleavage assays using purified recombinant RNase Y and artificial rpoS mRNA substrates and (2) constructing a strain of B. burgdorferi that expresses a recombinant RNase Y with a 10X-histidine tag in order to directly purify RNase Y