Molecular biology applied to parasitology: the ribosomal cistron as a tool in taxonomic and phylogenetic studies and as model for gene expression analysis

RESUMO

The singular sequence organization of ribosomal RNA encoding genes, consisting in the presence of highly conserved segments immersed in neutral evolving sequences, allowed its utilization as a tool for taxonomic and phylogenetic studies. In this communication a review of some contributions to related studies on Trypanosomatidae family organisms is presented. The desription of restriction maps for these genes led to the consequent description of probes useful for proper identification of the parasites. Better conditions for detection of parasites in samples from patients or from insect host vectors in endemic areas were established. On the other side, studies on basic concerns such as the regulation of gene expression, led to the determination of the promoter region for RNA Pol I of Trypanosoma cruzi. Sequence comparison with other trypanosomatid promoters did not show any consensus. However, the presence of elements in both promoter region and sequences upstream to the promoter indicated a possible transcription regulatory role for these elements. Transfection experiments showed that no enhancer activity is present.