Borrelia burgdorferi, the causative agent of Lyme disease, requires shifts in gene expression to undergo its natural enzootic cycle between tick and vertebrate hosts. mRNA degradation is an important mechanism for gene regulation, but is not yet characterized in B. burgdorferi. We propose to characterize the roles of specific ribonucleases in mRNA turnover by comparing the decay rates and steady state abundances of transcripts in wild-type and ribonuclease deficient strains of B. burgdorferi. We will determine the consensus sequences and structures of mRNA recognized and cleaved by ribonucleases. In order to gain insight into the relationship between translational regulation and mRNA decay for genes important in the enzootic cycle, we will examine the rates of mRNA decay of transcripts in the presence and absence of their translational regulators. The data from the proposed experiments will provide researchers with , will be the first to provide insight into the roles of individual ribonucleases, characteristics of ribonuclease cleavage sites, and relationships between translational regulation and mRNA decay for selected genes in this important pathogen. Lyme disease infects approximately 300,000 U.S. citizens each year. A better understanding of the molecular mechanisms of gene regulation, including those involving mRNA decay, that are used by this pathogen to survive the transition between vector and host is essential for the design of improved diagnostic and treatment strategies.
Borrelia burgdorferi, the causative agent of Lyme disease, has an enzootic life cycle alternating between Ixodes ticks and mammalian hosts, typically small rodents. Uninfected larval ticks acquire the bacteria by feeding on infected rodents. These ticks then remain infected and are capable of transmitting B. burgdorferi throughout their remaining developmental stages. Although humans are only inadvertently infected, Lyme disease remains the most common arthropod-borne disease in the United States; accounting for approximately 90% of all vector-borne disease cases. Lyme disease is also an emerging threat. The CDC estimated more than 300,000 cases in 2012. A vaccine directed against OspA, a major outer surface protein of B. burgdorferi, was developed, but it was eventually withdrawn from the market. Currently, no vaccine directed against B. burgdorferi is available for humans. Therefore, understanding the molecular mechanisms used by this pathogen to survive the transition between vector and host is essential for the design of improved diagnostic and treatment strategies. Genetic studies have revealed that differential gene regulation in the spirochete is essential for transmission between the tick vector and mammalian hosts, and mRNA degradation is an important part of gene regulation in other bacteria. However, the pathways of mRNA decay in Borrelia burgdorferi are not yet known. We propose to characterize mechanisms of mRNA decay in B. burgdorferi. The data from the proposed experiments will would bridge a knowledge gap in understanding how mRNA degradation functions in regulating gene expression.