RNA polymerase I-mediated protein-coding gene expression in Trypanosoma brucei

Protein-coding genes are transcribed by RNA polymerise (pol) II in all eukaryotes analyzed to date, with the exception of the protozoan Trypanosoma brucei, where pol I can mediate expression of chloramphenicol acetyl transferase (CAT) and neomycin phosphotransferase (neo) reporter genes. The addition of the capped 39-nucleotide (nt) mini-exon to the pre-messenger RNA (mRNA) by trans-splicing in T. brucei has presumably led to the uncoupling of the requirement for production of mRNA by pol II. Here Hui-min Chung, Mary G-S. Lee and Lex Van der Ploeg review the evidence that supports the notion that pol I also transcribes a subset of naturally occurring protein-coding genes in T. brucei.     

Molecular Comparison of the Mitochondrial and Cytoplasmic hsp 70 of Trypanosoma cruzi, Trypanosoma brucei and Leishmania major

ABSTRACT. We compared the expression and localization of the mitochondrial and cytoplasmic hsp70 of the protozoans Trypanosoma cruzi, Trypanosoma brucei and Leishmania major. The mitochondrial protein is encoded by multiple mRNA in all species, while the cytoplasmic protein is encoded by a single mRNA. In all three species, the mitochondrial hsp70 is concentrated in the kinetoplast, a submitochondrial structure that houses the unusual DNA (kDNA) that characterizes this group of organisms, while the cytoplasmic protein is distributed throughout the cell. These results suggest that, in all kinetoplastid species, mt-hsp70 has a specific function in kDNA biology, possibly in the processes of kDNA replication, RNA editing or kinetoplast structure.     

Anatomy of the parp gene promoter of Trypanosoma brucei.

While growing in the tsetse fly, Trypanosoma brucei expresses a major surface glycoprotein, the procyclic acidic repetitive protein (PARP). The parp genes are transcribed by an alpha-amanitin-resistant RNA polymerase. We have determined the sequence requirements for parp promoter activity. Studies of RNA produced from input DNA in transiently transfected trypanosomes indicate that the RNA is correctly processed by trans-splicing and polyadenylation. Deletion analyses show that 330 bp are sufficient for full promoter and splicing activity and that the promoter structure is complex, involving at least three elements whose mutual spacing is important. Mutagenesis pin-pointed two sequences vital for promoter activity; neither bears any resemblance to known prokaryotic or eukaryotic promoter elements.