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Microbiology and Molecular Genetics Program
B.Sc. 2006, Ursinus College
Thesis Advisor: Vivian Bellofatto, Ph.D.
Department of Microbiology and Molecular Genetics
Tuesday, May 22, 2012
11:00 A.M., ICPH Auditorium
Trypanosome RNA synthesis is unique from other eukaryotes in many ways. For example, most protein-encoding genes are transcribed as part of long polycistronic pre-mRNAs that are subsequently processed into mature monocistronic mRNAs. Each open reading frame of the original pre-mRNA can exhibit different steady state levels, indicating that post-transcriptional regulation is important for gene expression. Deadenylation is often the rate-limiting event in regulating the turnover of cellular mRNAs in eukaryotes. Removal of the poly(A) tail initiates mRNA degradation by one of several decay pathways, including 5’ to 3’ exonuclease decay and 3’ to 5’ exosome-mediated decay. Poly(A)-specific ribonuclease (PARN) is a key deadenylase involved in regulating gene expression in mammals, Xenopus oocytes, and higher plants. Trypanosomes possess three different PARN genes, PARN-1, -2, and -3. We predict that each PARN deadenylates a different subset of mRNAs. Therefore, we characterized PARN-1 and PARN-3 of human infective trypanosome Trypanosoma brucei. Western analysis indicates that PARN-1 and PARN-3 proteins are expressed in procyclic form and bloodstream form T. brucei cells. Fractionation of PARN-1 and PARN-3 indicate that both deadenylases are primarily cytoplasmic. Northern analysis indicates that over-expression of PARN-1 leads to faster deadenylation of epimastigote-stage surface proteins, called BARPs. Generation of a conditional parn-3 knockout cell line indicates that PARN-3 is not essential for procyclic form proliferation. Together these data further elucidate the role of PARN-1 and PARN-3 in T. brucei.