Identification of positive and negative regulators in the stepwise developmental progression towards infectivity in Trypanosoma brucei.

Trypanosoma brucei is a protozoan parasite that causes important human and livestock diseases in sub-Saharan Africa. By overexpressing a single RNA-binding protein, RBP6, in non-infectious procyclics trypanosomes, we previously recapitulated in vitro the events occurring in the tsetse fly vector, namely the development of epimastigotes and infectious, quiescent metacyclic parasites. To identify genes involved in this developmental progression, we individually targeted 86 transcripts by RNAi in the RBP6 overexpression cell line and assessed the loss-of-function phenotypes on repositioning the kinetoplast, an organelle that contains the mitochondrial genome, the expression of BARP or brucei alanine rich protein, a marker for epimastigotes, and metacyclic variant surface glycoprotein.

Molecular characterization of 5S ribosomal RNA genes and transcripts in the protozoan parasite Leishmania major.

Eukaryotic 5S rRNA, synthesized by RNA polymerase III (Pol III), is an essential component of the large ribosomal subunit. Most organisms contain hundreds of 5S rRNA genes organized into tandem arrays. However, the genome of the protozoan parasite Leishmania major contains only 11 copies of the 5S rRNA gene, which are interspersed and associated with other Pol III-transcribed genes.

Transcription of Leishmania major U2 small nuclear RNA gene is directed by extragenic sequences located within a tRNA-like and a tRNA-Ala gene.

Background: Leishmania and other trypanosomatid parasites possess atypical mechanisms of gene expression, including the maturation of mRNAs by trans-splicing and the involvement of RNA Polymerase III in transcription of all snRNA molecules. Since snRNAs are essential for trans-splicing, we are interested in the study of the sequences that direct their expression. Here we report the characterization of L.