Noreen Williams, Ph.D. Professor Department of Microbiology & Immunology Phone: (716) 829-2279 Fax: (716) 829-2158 Email: nw1@buffalo.edu

Developmental 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. Two projects focus on Trypanosoma brucei, the causative agent of African sleeping sickness, which is transmitted by the tse-tse fly. A third project focuses on Trypanosoma cruzi, which causes Chagas’ disease in South and Central America and is transmitted by the reduviid bug. Treatment for these diseases are severely limited due to increasing drug resistance and issues of drug toxicity or they are not available at all. The goal of our work is to discover and exploit regulatory events that occur in the parasite life cycle that may be used to prevent growth or transmission of the parasite.

The first project centers on the mitochondrial ATP synthase of T. brucei. This protein complex couples the energy generated by the electron transport chain to the synthesis of ATP. In T. brucei we have shown that the ATP synthase is regulated through the life cycle of the organism by several unique mechanisms which appear to be different from the regulatory mechanisms for other mitochondrial proteins such as those in the electron transport chain. This regulation may be critical to understanding how this parasite responds to change in the environment due to the two host organisms (in this case, the tsetse fly and the cow). We have isolated the ATP synthase and have cloned several genes for component subunits of the complex. We have shown a differential regulation of these subunits at the level of mRNA stability and are now examining the specific sequences and nucleic acid binding proteins involved in this regulation. We are using RNA interference to create genetic knock downs as a tool to understanding the role of the ATP synthase in the parasites survival in its hosts. Our recent data shows that the ATP synthase is responsible for maintaining a membrane potential in the bloodstream stage of the parasite. This membrane potential is required for the parasite’s survival since without it the parasite cannot pre-adapt for survival in the insect vector. These results suggest that the ATP synthase may provide an excellent target for drug development focused on preventing transmission of the parasite by the insect.

The second project, in collaboration with Dr. William Ruyechan, examines a pair of unique RNA binding proteins, p34 and p37, which are highly homologous to one another. We have shown that these proteins interact with 5 S rRNA and hypothesize that they act to chaperone the 5 S rRNA from the nucleus where it is synthesized by RNA polymerase III, to the nucleolus for assembly with other ribosomal components. We have also identified a family of nucleolar phosphoproteins, the NOPP44/46 proteins, that interact with the p34 and p37 proteins, and may assist in this process of 5S rRNA migration. The p34 and p37 proteins show developmentally regulated expression through the life cycle of T. brucei. Most interestingly, the regulation of the two proteins are exactly opposite one another making them an excellent target to examine developmentally regulated genes. Expression of the smaller of the two proteins, p34, is regulated by differential mRNA stability and we have found two AU rich sequence elements present in the 3' untranslated region of this transcript that may be responsible. These AU rich elements have been shown in higher eukaryotes to be involved in both transcript stability and translational regulation. In constrast, expression of the larger protein, p37, is regulated translationally, possibly by sequences in the 3' untranslated region as well. In addition, we have found that the p37 protein is specifically degraded in the procyclic stage of the parasite and are currently characterizing the protease responsible for this process.

In collaboration with Dr. Beatriz Garat, Universidad de la Républica, Dept. of Biochemistry, Montevideo, Uruguay, we are examining proteins which bind to dinucleotide repeats occurring in the intergenic regions of the genome of Trypanosoma cruzi. This project, which is funded by the Fogarty Foundation, examines whether these repeats together with their cognate binding proteins may be involved in gene regulation in T. cruzi.

Williams Lab
Back Row: Paul Gulde, Will Murtaugh, Martin Ciganda, Haiming Wu
Middle Row: Bing Wang, Silvia Brown B., Noreen Williams, Charity McManaman, Kim Prohaska
Front Row: Alma Velayo, Lei Wang

Research and Professional Experience:

Professor [2002- present], Associate Professor [1998 - 2002], and Assistant Professor [1992 - 1998] Department of Microbiology, School of Medicine and Biomedical Sciences, University at Buffalo

Assistant Professor, Department of Biochemistry, Uniformed Services University of the Health Sciences, Bethesda, MD, 1987-1992

Postdoctoral Fellow/Research Associate, The McCollum-Pratt Institute and Department of Biology, Johns Hopkins University, Baltimore, MD, l984-1987, Research Advisor: Dr. Saul Roseman

Postdoctoral Fellow, Department of Biological Chemistry, Johns Hopkins University School of Medicine, Baltimore, MD, 1981-1984, Research Advisor: Dr. Peter L. Pedersen

Professional Activities:

Chair, 2005-6 and member [2004-6] NIH Pathogenic Eukaryotes [formerly TMP] Study Section

Chair [2000-2001] and member [1996-2001], ad hoc [2001- present] NIH International and Cooperative Projects Study Section

Chair, NIH ICP Special Emphasis, Global Research Initiatives Program, 2002, 2003

Member, 2002-4 and ad hoc [2000], NIH Tropical Medicine and Parasitology Study Section

Wellcome Trust Reviewer [ ad hoc ] 1999, 2002, 2003

Member, Editorial Board, Journal of Bioenergetics and Biomembranes, 1991-present Peer Reviewer ( ad hoc ), J. Biological Chemistry, Mol. Biochem. Parasitol., Can. J. Physiology and Pharmacology, J. Euk. Microbiology, Molecular and Cell Biology, Eukaryotic Cell

Ellison Visiting Scholar, Marine Biological Laboratories, 2003

National Research Service Award, National Institute of General Medical Sciences, 1984-1986

Relevant Publications:

Brown B., S.V., Stanislawski, A., Perry, Q. L., and Williams, N . (2001) Cloning and characterization of the subunits comprising the catalytic core of the Trypanosoma brucei ATP synthase Mol. Biochem. Parasitol. 113:289-301.

Brown B., S.V., Chi, T.B., and Williams, N. (2001) The mitochondrial ATP synthase is developmentally regulated at the level of transcript stability. Mol. Biochem. Parasitol .15: 177-187.

Pitula, J., Ruyechan, W.T., and Williams, N . (2002) Two novel RNA binding proteins from T. brucei are associated with 5S rRNA Biochem. Biophys. Res. Commun . 290: 569-576 .

Pitula, J., Park, J., Parsons, M., Ruyechan, W.T., and Williams, N . (2002) Two families of RNA binding proteins in T. brucei associate in a direct protein-protein interaction. Mol. Biochem. Parasitol . 122: 77-85.

Li, J. Ruyechan, W.T., and Williams, N . (2003) Stage specific translational efficiency and protein stability regulate the developmental expression of p37, an RNA binding protein from Trypanosoma brucei . Biochem. Biophys. Res. Commun. 306: 918-923.

Duhagon, M.A., Dallagiovanna, B., Ciganda, M., Ruyechan, W., Williams, N ., and Garat, B. (2003) A novel type of single-stranded nucleic acid binding protein recognizing a highly frequent motif in the intergenic regions of Trypanosoma cruzi . Biochem. Biophys. Res. Commun. 309: 183-188.

Gomes, G., Ürményi, T., Rondenelli, E., Williams, N ., and Silva, R. (2004) RNA binding proteins TcRRM1 and TcRRM2 and an unknown gene Tc28 are intercalated in the genome and are differentially expressed during the life cycle of Trypanosoma cruzi . Biochem. Biophys. Res. Commun. 322: 985-992.

Brown, S.V., Hosking, P., Li, J.L., and Williams, N . (2006) The Mitochondrial ATP Synthase is responsible for maintenance of membrane potential in bloodstream T. brucei . Euk. Cell 5: 45-53.

Hellman, K., Brown, S.V., Ciganda, M., Li, J.L., Ruyechan, W.T., and Williams N (2006) Two trypanosome-specific proteins are essential factors for 5S rRNA stability and translation in T. brucei [in revision]

Wu, H., Li, J., and Williams, N . AU rich elements mediate mRNA stability and developmental regulation for an RNA binding protein, p34, in Trypanosoma brucei [in submission]

Wu, H., Wang, B., and Williams, N. (2006) Trypanosoma brucei HMG-like TDP-1 protein selectively binds to different 3' UTR sequences [in submission]

Hellman, K., Prohaska, K., and Williams, N. (2006) T. brucei RNA binding proteins, p34 and p37, mediate NOPP44/46 localization through a protein-protein interaction. [in submission ]