RNA TRANSSPLICING IN FLATWORMS - ANALYSIS OF TRANS-SPLICED MESSENGER-RNAS AND GENES IN THE HUMAN PARASITE, SCHISTOSOMA-MANSONI

Characteristics of trans-splicing in Schistosoma mansoni were examined to explore the significance and determinants of spliced leader (SL) a ddition in flatworms. Only a small subset of mRNAs acquire the SL. Ana lysis of 30 trans-spliced mRNAs and four genes revealed no discernable patterns or common characteristics in the genes, mRNAs, or their enco ded proteins that might explain the functional significance of SL addi tion. While the mRNA encoding the glycolytic enzyme enolase is trans-s pliced, mRNAs encoding four other glycolytic enzymes are not, indicati ng trans-splicing is not prevalent throughout this metabolic pathway. Although the 3' end of flatworm SLs contribute an AUG to mRNAs, the SL AUG does not typically serve to provide a methionine for translation initiation of reading frames in recipient mRNAs. SL RNA expression exh ibits no apparent sex, tissue, or cell specificity. Trans-spliced gene s undergo both cis- and trans-splicing, and the sequence contexts for these respective acceptor sites are very similar. These results sugges t trans-splicing in flatworms is most Likely associated either with so me property conferred on recipient mRNAs by SL addition or related to some characteristic of the primary transcripts or transcription of tra ns-spliced genes.