Research Interests
My research program has two foci: the expression, maturation, and function of the spliced leader (SL) RNA in Leishmania and Trypanosoma, and genetic variability in Trypanosoma cruzi. These organisms are agents of disease in humans. Both of my studies began with the examination of the SL RNA gene, the product of which is trans-spliced onto every nuclear mRNA in a process absent from their hosts. We have established a model for SL RNA transcription and processing. The SL RNA gene contains the only RNA polymerase II promoter identified to date, and we are identifying associated transcription factors. We provided direct evidence for nuclear export and cytosolic processing of the SL RNA with our characterization of the Exportin 1 gene (Zeiner et al., 2003, EC) and RNA inhibition studies of the SmD1 protein (Zeiner et al., 2004, EC). Our current studies focus on the identification of SL RNA processing enzymes (e.g., 3′ exonuclease SNIP in Zeiner et al., 2004, MCB). One of the more elusive questions concerned the function of highly conserved sequences within the SL. Our previous studies have shown that neither transcription (Saito et al., 1994) nor trans-splicing (Sturm et al., 1998) were affected by mutagenesis of conserved portions of SL. We have now shown that the SL mediates the association of mRNA with ribosomes, and hence possesses a role in translation (Zeiner et al., 2003, JBC). We continue to explore interactions of spliced SL with the translation machinery. The perceived population structure of T. cruzi, the causative agent of Chagas disease, has varied between two and 43 distinct lines over the past few decades. Currently, six groups are thought to be biologically significant and potentially relevant to disease manifestation. We have shown that four of these are hybrid subgroups display variable levels of genetic exchange between two original ‘parental’ lineages (Sturm et al., 2003). Continued examination of molecular markers indicates that two of these subgroups are nearly identical (Westenberger et al., 2005, Genetics). This project has been expanded to the genome level; in addition to the strain CL Brenner, which is a heterozygous hybrid at most individual loci examined, a parental strain of T. cruzi was sequenced. We have assembled the mitochondrial maxicircle sequences from the two strains (Westenberger et al., 2006, BMC Genomics) in the continued quest for markers.