Trichomonas vaginalis ribosomal RNA: Identification and characterisation of the transcription promoter and terminator sequences

Trichomonas vaginalis is a parasitic protozoan of both medical and biological relevance. Transcriptional studies in this organism have focused mainly on type II pol promoters, whereas the elements necessary for transcription by polI or polIII have not been investigated. Here, with the aid of a transient transcription system, we characterised the rDNA intergenic region, defining both the promoter and the terminator sequences required for transcription. We defined the promoter as a compact region of approximately 180 bp. We also identified a potential upstream control element (UCE) that was located 80 bp upstream of the transcription start point (TSP). A transcription termination element was identified within a 34 bp region that was located immediately downstream of the 28S coding sequence. The function of this element depends upon polarity and the presence of both a stretch of uridine residues (U's) and a hairpin structure in the transcript. Our observations provide a strong basis for the study of DNA recognition by the polI transcriptional machinery in this early divergent organism.

Graphical abstractpolI transcription of ribosomal RNA in Trichomonas vaginalis is driven by a compact promoter and a terminator containing a stretch of uridines and a stem-loop structure.Figure optionsDownload full-size imageDownload high-quality image (62 K)Download as PowerPoint slideHighlight► Transcription of the rRNA genes in Trichomonas vaginalis. ► Compact polI promoter containing a potential upstream control element (UCE). ► Terminator sequence of 34 nucleotides downstream of the 28S coding sequence. ► Terminator function depends upon a stretch of U's and a hairpin structure.