Department of Microbiology and Immunology
Eukaryotic Pathogenesis; Gene Expression; Infectious Disease; Microbial Pathogenesis; Microbiology; Molecular and Cellular Biology; Molecular Basis of Disease; Protein Function and Structure; Regulation of metabolism; RNA; Transcription and Translation
Regulation of Gene Expression in Trypanosomes
Our laboratory uses molecular biological and biochemical approaches to study a group of parasitic protozoans that cause disease in humans and domestic animals in much of the tropical world. The major project focuses on Trypanosoma brucei, the causative agent of African sleeping sickness, which is transmitted by the tse-tse fly. Other projects focus on Trypanosoma cruzi, which causes Chagas disease in South and Central America and is transmitted by the reduviid bug. Treatment for these diseases is severely limited due to increasing drug resistance and issues of drug toxicity or lack of available drugs. The goal of our work is to discover and exploit critical events that occur in the parasite life cycle that may be used to prevent growth or transmission of the parasite.
The major project in the laboratory examines the ribosome, the complex molecular machine that drives protein synthesis. While many features of the ribosome and its assembly pathway are conserved in the parasites we study, we have identified a number of features in this pathway that are very different from the pathway in the human host. Our laboratory discovered a pair of trypanosome-specific RNA binding proteins, P34 and P37, which are essential to the formation of ribosomes only in these parasites. We have shown that these proteins interact with 5S rRNA and ribosomal protein L5 in a unique pre-ribosomal complex that is essential for ribosomal biogenesis and survival of the trypanosomes. Perhaps due to the presence of the trypanosome-specific proteins, P34 and P37, the normally conserved L5 protein also possesses unusual structural and functional characteristics. In addition, we have shown that P34 and P37 are required for the export of the large ribosomal subunit from the nucleus to the cytoplasm where it assembles into the fully functional ribosome required for protein synthesis.
The multiple roles of these trypanosome-specific proteins in the normally highly conserved pathway of ribosomal biogenesis is a surprising finding and may suggest that the interaction of these proteins with other components of the ribosomal assembly pathway can be developed as targets for chemotherapy. We have developed a fluorescence resonance energy transfer assay that allows us to study these interactions more closely. This method also allows us to develop a high throughput screen for small molecules that disrupt the complex in trypanosomes and do not harm the human host. Since little is known about the ribosome in trypanosomes, we are current collaborating in a project to examine the structure of the ribosome and intermediates in the pathway of assembly using cryo-EM. These experiments will provide important information about the unique features of the structure and function of the trypanosome ribosome. These studies will increase our understanding of the basic biology of the ribosome and further our discovery of potential drug targets.
More recently we have begun work characterizing this complex in the related parasite, T. cruzi with the idea that we may be able to use a similar approach to develop chemotherapeutic targets that would apply to the two related parasites, T. brucei and T. cruzi . In addition, we continue in a long standing collaboration with Dr. Beatriz Garat at the Universidad de la Républica in Uruguay, examining both DNA and RNA binding proteins which regulate gene expression in Trypanosoma cruzi.