Characterization of a SR protein from Trypanosoma brucei with homology to RNA-binding cis-splicing proteins

The protozoan parasite Trypanosoma brucei relies on trans-splicing to proce ss its mRNAs. A novel nuclear serine/arginine (SR)-rich trypanosomal protei n (TSR1) was characterized which contains two RNA recognition motifs. The T SR1 protein appears to be homologous to RNA-binding SR proteins of the cis- splicing machinery from higher eukaryotes. Moreover, in the yeast two-hybri d system, TSR1 is able to interact with the human splicing factors involved in the recognition of the 3' splicing site (U2AF35/U2AF65). In both procyc lic and bloodstream forms of T. brucei, TSR1 was found to localize in the n ucleus. In the bloodstream stage TSR1 showed the speckles pattern character istic of SR proteins involved in cis-splicing. Moreover, TSR1 was able to s pecifically bind the spliced leader (SL) RNA involved in trans-splicing in trypanosomes by the yeast three-hybrid system. These and other observations suggest that TSR1 may be involved in traits-splicing in T. brucei. (C) 199 9 Elsevier Science B.V. All rights reserved.