A NEW VSG EXPRESSION SITE-ASSOCIATED GENE (ESAG) IN THE PROMOTER REGION OF TRYPANOSOMA-BRUCEI ENCODES A PROTEIN WITH 10 POTENTIAL TRANSMEMBRANE DOMAINS

In Trypanosoma brucei bloodstream variants 118 cl 1, 118a and 118b, the actively transcribed VSG gene expression site (ES) is located on a 1.5 Mb chromosome. The promoter region for this polycistronic transcription unit is unusual in that there are two, tandemly located, promoter repeats, each 2.1 kb in size, separated by 13 kb of intervening DNA. As previously shown, at inactivation of this ES, the promoter region was rearranged with the deletion of 15 kb of DNA. This result prompted us to search through the deleted DNA sequences to identify additional genes that might play a role in the inactivation of ESs. In this report, we identify a gene, encoding a putative transmembrane protein, that was deleted at this locus by the rearrangement event. This gene, which we tentatively call expression-site-associated-gene 10 (ESAG10), contains 10 potential transmembrane domains and had been located to T. brucei stock 427-60, ES-containing chromosomes.