David A. Campbell

Work Address:
Dept. Microbiology, Immunology & Molecular Genetics
4821 Molecular Sciences Building
605 Charles E. Young Drive East
University of California
Los Angeles, CA 90095 Dept. Microbiology, Immunology & Molecular Genetics
4825 Molecular Sciences Building
605 Charles E. Young Drive East
University of California
Los Angeles, CA 90095

Affiliations
Affiliations
Professor, Microbiology, Immunology & Molecular Genetics
Member, Immunity, Microbes & Molecular Pathogenesis GPB Home Area, Molecular Biology Institute
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.
Biography

Gene expression and variability in Kinetoplastid protozoa 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., In Press). Our current studies focus on the identification of SL RNA processing enzymes. We are initiating the use of localized ribozymes to track SL RNA movement. 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, Sturm and Campbell, in preparation). This project is being expanded to the genome level in a collaboration with The Institute for Genome Research; in addition to the strain CL Brenner, which is a heterozygous hybrid at most individual loci examined, two additional parental strains of T. cruzi will be sequenced.

Publications
Zeiner, G.M., Foldynova, S., Sturm, N.R., Luke_, J. and Campbell, D.A. SmD1 is required for Spliced Leader RNA biogenesis. Eukaryotic Cell 2004; 3: 241-244.
Campbell, DA Westenberger, SJ Sturm, NR The determinants of Chagas disease: connecting parasite and host genetics. Current molecular medicine. . 2004; 4(6): 549-62.
Zeiner, GM Sturm, NR Campbell, DA The Leishmania tarentolae spliced leader contains determinants for association with polysomes. The Journal of biological chemistry. . 2003; 278(40): 38269-75.
Zeiner, GM Sturm, NR Campbell, DA Exportin 1 mediates nuclear export of the kinetoplastid spliced leader RNA. Eukaryotic cell. . 2003; 2(2): 222-30.
Campbell, DA Thomas, S Sturm, NR Transcription in kinetoplastid protozoa: why be normal?. Microbes and infection / Institut Pasteur. . 2003; 5(13): 1231-40.
Yu, MC Orlando, TC Sturm, NR Zhou, L Saito, RM Floeter-Winter, LM Campbell, DA Two distinct functional spliced leader RNA gene arrays in Leishmania tarentolae are found in several lizard Leishmania species. International journal for parasitology. . 2002; 32(11): 1411-22.
Campbell, DA Sturm, NR Yu, MC Transcription of the kinetoplastid spliced leader RNA gene. Parasitology today. 2000; 16(2): 78-82.
Sturm, NR Yu, MC Campbell, DA Transcription termination and 3'-End processing of the spliced leader RNA in kinetoplastids. Molecular and cellular biology. . 1999; 19(2): 1595-604.
Fernandes, O., Mangia, R., Lisboa, C.V., Pinho, A.P., Morel, C.M., Zingales, B., Campbell, D.A. and Jansen, A.M. The complexity of the sylvatic cycle of Trypanosoma cruzi in Rio de Janeiro state (Brazil) revealed by the non-transcribed spacer of the mini-exon gene. Parasitology 1999; 181: 161-166.
Yu, MC Sturm, NR Saito, RM Roberts, TG Campbell, DA Single nucleotide resolution of promoter activity and protein binding for the Leishmania tarentolae spliced leader RNA gene. Molecular and biochemical parasitology. . 1998; 94(2): 265-81.
Fernandes, O Teixeira, MM Sturm, NR Sousa, MA Camargo, EP Degrave, WM Campbell, DA Mini-exon gene sequences define six groups within the genus Crithidia. The Journal of eukaryotic microbiology. . 1997; 44(6): 535-9.