Affinity purification of Trypanosoma brucei small nuclear ribonucleoproteins reveals common and specific protein components.

We have developed a procedure for the affinity purification of small nuclear ribonucleoproteins (snRNPs) of Trypanosoma brucei (U2 and U4/U6 snRNPs), which are essential for trans splicing. Each of these snRNPs can be specifically and efficiently selected from T. brucei extracts through biotinylated antisense 2'-O-methylated RNA oligonucleotides immobilized on streptavidin-agarose. Protein analysis revealed a set of five low molecular weight polypeptides common to the U2 and U4/U6 snRNPs and the spliced leader RNP. In addition, several U2 and U4/U6 snRNP-specific protein components were identified. Using monoclonal antibodies against human snRNP proteins, we could not detect any significant cross-reaction with the trypanosomal U2 snRNP proteins. Thus, the trypanosomal snRNPs exhibit principal differences from the higher eukaryotic snRNPs not only in their RNA but also in their protein components.