Discussion

The nuclear pore complex (NPC) is responsible for multiple processes, including nucleocytoplasmic transport, interactions with the nuclear lamina and mRNA processing, and thus constitutes a hub for the control of gene expression. Remarkably, despite retaining similar protein compositions, there are exceptional architectural dissimilarities between yeast and vertebrate and trypanosome NPCs. Whilst elements of the inner core are conserved, numerous peripheral structures are highly divergent, perhaps reflecting requirements to interface with divergent nuclear and cytoplasmic functions. Moreover, the trypanosome NPC has almost complete nucleocytoplasmic symmetry, in contrast to the fungal and animal NPC and a remarkable absence of components involved in mRNA export in fungi and animals. Concomitant with this, we find evidence supporting Ran-dependent mRNA export in trypanosomes, similar to protein transport, whilst in animals and fungi mRNA export is Ran-independent. Identification of these lineage-specific features suggests that despite an overall well conserved structure, several aspects that differentiate the trypanosome NPC and suggest significant divergence in mRNA export mechanics.