The trypanosome undergoes antigenic variation, in which the VSG can be changed to a new type hundreds of times during infection. We have shown that M-VSG genes are regulated in a very interesting way, using promoters, subject to regulation by transcriptional activation, located very close to chromosome ends.
Regulation is determined partly by the locus itself.
We are studying the complex promoter structure and the regulatory role of the locus, including the telomere. Image shows alternate routes for activation of the 1.22 VSG gene we study. When activated in the tsetse fly, as shown here by immunofluorescence of the trypanosome surface, the gene is transcriptionally activated in its own locus. In the bloodstream, however, it is activated only by being duplicated into a complex, polycistronic transcription unit. Please click on the image to magnify.