Fig. 10: Model of the architecture of the Expression Site nuclear body assembly in BF T. brucei.
From: An assembly of nuclear bodies associates with the active VSG expression site in African trypanosomes
Schematic representation of a BF T. brucei nucleus (light blue) with the nucleolus indicated (dark blue). Active and silent ESs are expanded in the green boxes. The active ES is associated with four discrete nuclear bodies: The ESB (green circle), the Cajal body (dark blue circle), the SLAB (red circle) and the NUFIP body (purple circle). The ESB contains Pol I and VEX2, and shows partial overlap with a highly SUMOylated focus (SUMO). The SLAB closely associates with the spliced leader (SL) RNA gene locus. The ESs contain various genes (white boxes) in addition to the telomeric VSG gene, with the promoters indicated with flags, transcription with a red arrow and telomere repeats with black triangles. These four nuclear bodies appear to often cluster in a single nuclear compartment which forms an ES nuclear body assembly (large light-blue circle with red dashed outline) satisfying the high demand for splicing at the active ES. Silent ESs are not associated with this ES nuclear body assembly and the low amount of nascent RNA generated from these ESs is not spliced efficiently.
