Figure 1

Isolation of trypanosome BESs in yeast using Transformation Associated Recombination (TAR) cloning as described in[34]. A schematic of a typical BES is shown above with the promoter indicated with a flag, and different expression site associated genes (ESAGs) indicated with coloured boxes. Characteristic repeat arrays either upstream of the BES promoter (50 bp repeats) or adjacent to the telomeric VSG gene (70 bp repeats) are indicated with vertically hatched boxes. Trypanosome telomere repeats are indicated with white arrows. The linearised pEB4 TAR vector is shown below with yeast telomere repeats (black triangles) as well as a positive (+) and a negative (-) selectable marker flanking a BES promoter containing fragment. Recombination between the vector and genomic DNA on the BES promoter fragment results in a yeast artificial chromosome (YAC) which can be stably maintained.