Potential regulatory elements in the Trypanosoma cruzi rRNA gene promoter

The Trypanosoma cruzi rRNA gene promoter was characterized by deletion and point mutation analyses. A core of 89 bp was identified as the minimal region with full promoter activity. This core region is flanked upstream by a control element that stimulates its activity, and downstream by a novel down regulating region of about 200 bp. A point mutation analysis of the transcription start region evidenced 7 contiguous nucleotides where individual substitutions produced in all cases a defective promoter. It is generally accepted that the anciently speciated trypanosomatids lack strict promoters for protein coding genes transcribed by RNA polymerase II. The occurrence of a well structured rRNA gene promoter in these species suggests an early appearance of the RNA polymerase I promoters in the evolution of eukaryotic cells.