ABSTRACT
The Telomeric Repeat-containing RNAs (TERRA) participate in the homeostasis of telomeres in higher eukaryotes. Here, we investigated the expression of TERRA in Leishmania spp. and Trypanosoma brucei and found evidences for its expression as a specific RNA class. The trypanosomatid TERRA are heterogeneous in size and partially polyadenylated. The levels of TERRA transcripts appear to be modulated through the life cycle in both trypanosomatids investigated, suggesting that TERRA play a stage-specific role in the life cycle of these early-branching eukaryotes.
Subject(s)
Trypanosoma brucei brucei/genetics , RNA/genetics , Repetitive Sequences, Nucleic Acid/genetics , Telomerase/genetics , Leishmania/geneticsABSTRACT
The kinetoplast genetic code deviates from the universal code in that 90 percent of mitochondrial tryptophans are specified by UGA instead of UGG codons. A single nucleus-encoded tRNA Trp(CCA) is used by both nuclear and mitochondria genes, since all kinetoplast tRNAs are imported into the mitochondria from the cytoplasm. To allow decoding of the mitochondrial UGA codons as tryptophan, the tRNA Trp(CCA) anticodon is changed to UCA by an editing event. Two tryptophanyl tRNA synthetases (TrpRSs) have been identified in Trypanosoma brucei: TbTrpRS1 and TbTrpRS2 which localize to the cytoplasm and mitochondria respectively. We used inducible RNA interference (RNAi) to assess the role of TbTrpRSs. Our data validates previous observations of TrpRS as potential drug design targets and investigates the RNAi effect on the mitochondria of the parasite.
Subject(s)
Animals , RNA Interference , RNA, Protozoan/metabolism , RNA, Transfer/metabolism , Trypanosoma brucei brucei/enzymology , Tryptophan-tRNA Ligase/metabolism , Gene Expression , RNA, Protozoan/genetics , RNA, Transfer/genetics , Time Factors , Trypanosoma brucei brucei/cytology , Trypanosoma brucei brucei/genetics , Tryptophan-tRNA Ligase/geneticsABSTRACT
Mechanisms controlling gene expression in trypanosomatids depend on several layers of regulation, with most regulatory pathways acting at a post-transcriptional level. Consequently, these parasites can follow the rapid changes associated with transitions between the insect vector and the mammalian host, with instant reprogramming of genetic expression. Using primarily Trypanosoma brucei as a model, the basic controlling mechanisms have been elucidated and now researchers are beginning to define the cellular factors involved in the transcription, processing and translation of the mRNAs in these parasites. We describe some of the studies made on a subset of genes that are differentially expressed during the life cycles of T. brucei and T. cruzi. It is becoming evident that the regulatory strategies chosen by different species of trypanosomatids are not the same, and therefore, the lessons learned from one species do not necessarily apply to the others. Some of the tools available for genetic manipulation that have been developed along with these studies are also described. Two of them are of particular interest in this postgenomic period: inducible systems to express foreign genes and specific inhibition of gene expression by RNA interference
Subject(s)
Animals , Gene Expression Regulation , Genes, Protozoan , Trypanosomatina/genetics , Antigens, Protozoan/genetics , Antigens, Protozoan/metabolism , Membrane Glycoproteins/genetics , Membrane Glycoproteins/metabolism , RNA Interference , Trypanosoma brucei brucei/genetics , Trypanosoma brucei brucei/immunology , Trypanosoma brucei brucei/pathogenicity , Antigenic Variation/geneticsABSTRACT
The study of mechanisms which control gene expression in trypanosomatids has developed at an increasing rate since 1989 when the first successful DNA transfection experiments were reported. Using primarily Trypanosoma brucei as a model, several groups have begun to elucidate the basic control mechanisms and to define the cellular factors involved in mRNA transcription, processing and translation in these parasites. This review focuses on the most recent studies regarding a subset of genes that are expressed differentially during the life cycle of three groups of parasites. In addition to T. brucei, I will address studies on gene regulation in a few species of Leishmania and the results obtained by a much more limited group of laboratories studying gene expression in Trypanosoma cruzi. It is becoming evident that the regulatory strategies chosen by different species of trypanosomatids are not similar, and that for these very successful parasites it is probably advantageous to employ multiple mechanisms simultaneously. In addition, with the increasing numbers of parasite genes that have now been submitted to molecular dissection, it is also becoming evident that, among the various strategies for gene expression control, there is a predominance of regulatory pathways acting at the post-transcriptional level
Subject(s)
Animals , Antigenic Variation , Gene Expression Regulation , Transcription, Genetic , Trypanosomatina/genetics , Genes, Protozoan , Leishmania/genetics , Leishmania/immunology , Protozoan Infections/genetics , Trypanosoma brucei brucei/genetics , Trypanosoma brucei brucei/immunology , Trypanosoma cruzi/genetics , Trypanosoma cruzi/immunology , Variant Surface Glycoproteins, Trypanosoma/geneticsABSTRACT
The study of Trypanosoma cruzi type II DNA-topoisomerase should provide new clues for the rational development of new drugs for the chemotherapy of Chagas' disease. This enzyme is very likely involved in the processes leading to T. cruzi replication and differentiation since both processes are blocked by bacterial type II DNA topoisomerase inhibitors. In this article, we review and discuss our recent data related to the cloning, sequencing, and expression of T. cruzi type II topoisomerase