Identification of a nuclear protein in Trypanosoma brucei with homology toRNA-binding proteins from cis-splicing systems

Gene expression in trypanosomes is controlled at the level of pre-mRNA matu ration via trans-splicing and polyadenylation and through changes in mRNA s tability. To identify the trans- acting factors involved in this regulation , we have used a degenerate PCR approach to clone genes encoding the RNA re cognition motif (RRM) consensus. We have identified a single-copy gene enco ding a protein (designated RRM1) which contains three consensus RRM motifs, two tandem copies of a retroviral gag- like CCHC 'zinc finger' and an argi nine-serine (RS) rich region. Western blotting indicates that RRM1 is expre ssed in both procyclic and bloodstream-form trypanosomes and has an apparen t mobility on SDS-PAGE of ca. 70 Kd. RRM1 is localized in the trypanosome n ucleus in substructures which may be functionally analogous to the 'speckle s' associated with cis-splicing in higher eukaryotic cells. The structure o f RRM1, its pattern of expression and its intracellular location suggest th at it may play a role in trans-splicing. (C) 1998 Elsevier Science B.V. All rights reserved.