Evidence supporting a major promoter in the Trypanosoma cruzi rRNA gene

Two clearly separated transcription start points (tsp) have been reported within the Trypanosoma cruzi rDNA (DNA encoding rRNA) gene spacer region. These sites are separated by 270 bp, a distance compatible with the occurrence of two core promoters. To characterize the individual participation of these two elements, a deletion analysis was carried out. Different versions of the promoter regions were assayed in a transient transfection analysis of epimastigotes, using the chloramphenicol acetyl transferase gene (cat) as a reporter. The data indicate that the so-called distal tsp-associated region (relative to the small subunit rRNA 5' terminus coding region) comprises most (80%) if not all of the observed activity. In addition, an associated locus specific repeated element showed a modest upregulating activity, since its presence stimulated the cat reporter gene by about 20%. The data here presented should be valuable in the design of expression vectors for T. cruzi, where the rRNA gene promoter has been an important functional element.