Search for promoters for the GARP and rRNA genes of Trypanosoma congolense

A search was conducted for transcriptional promoters in Trypanosoma congole nse. A promoter test plasmid was constructed utilising the luciferase codin g region flanked by the intergenic regions of a T. congolense gene encoding GARP, the glutamic acid and alanine rich protein on the surface of procycl ic organisms. Using this plasmid; sequences located upstream of an 18S rRNA gene were tested in transient transfection assays for their ability to pro mote luciferase expression. A rRNA promoter fragment of 377 bp was identifi ed that increases luciferase activity by as much as 35 000-fold above backg round levels. The rRNA transcription initiation site is located 961 bp upst ream of the 18S rRNA gene and immediately downstream of 6 bp imperfect repe ats. The plasmid was also used to examine sequences upstream of a GARP gene cluster in two different T. congolense strains for promoter activity. In c ontrast to the findings of another group, we were unable to detect promoter activity upstream of these GARP genes in either strain. We conclude that t he GARP gene promoter, if it exists, has less than 0.03% (1/3000) of the ac tivity of the rRNA promoter in this luciferase-based assay. (C) 1999 Elsevi er Science B.V. All rights reserved.