Gene linkage and steady state RNAs suggest trans-splicing may be associated with a polycistronic transcript in Schistosoma mansoni

Mol Biochem Parasitol. 1997 Oct;89(1):25-39. doi: 10.1016/s0166-6851(97)00097-2.


Spliced leader (SL) trans-splicing generates the 5' end of mature mRNAs through the addition of a small exon to pre-mRNAs in some flagellates (kinetoplastida and euglenoids) and metazoans (nematodes and flatworms). Although SL addition in the kinetoplastida and a subset of nematode genes serves to resolve multicistronic mRNAs into monocistronic, capped mRNAs, information regarding the functional significance of trans-splicing in flatworms is limited. We describe here the identification and characterization of a closely linked gene upstream from the trans-spliced enolase gene in the flatworm Schistosoma mansoni. This gene produces a non-trans-spliced mRNA encoding a ubiquinol binding protein, UbCRBP, that is a component of the ubiquinol-cytochrome C reductase complex. The distance between the UbCRBP polyadenylation site and the enolase trans-splice acceptor site is exceptionally short, only 54 nucleotides. Primer extension (5' RACE), RT-PCR, and RNase mapping have identified steady state, cis-spliced RNAs which significantly overlap both the UbCRBP and enolase genes. These transcripts contain the 5' ends of mature UbCRBP mRNAs; extend through UbCRBP, across the intergenic region, and a significant distance 3' into the enolase gene. Interestingly, the close linkage between the UbCRBP and enolase genes is conserved in a second flatworm, Fasciola hepatica, which also trans-splices the downstream enolase gene. Taken together, the role of SL addition in resolving multicistronic transcripts in both C. elegans and the kinetoplastida, the conservation of UbCRBP/enolase gene linkage in two divergent trematodes, and the multicistronic organization of schistosome UbCRBP/enolase RNAs are consistent with the suggestion that these two genes are likely to be cotranscribed and that trans-splicing in flatworms may be associated with polycistronic transcripts.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Carrier Proteins / metabolism
  • Electron Transport Complex III / genetics
  • Fasciola hepatica / enzymology
  • Fasciola hepatica / genetics
  • Gene Amplification
  • Genes, Helminth*
  • Genetic Linkage*
  • Molecular Sequence Data
  • Phosphopyruvate Hydratase / genetics
  • RNA Splicing*
  • RNA, Messenger / chemistry
  • RNA, Messenger / genetics*
  • Ribonucleases
  • Schistosoma mansoni / enzymology
  • Schistosoma mansoni / genetics*
  • Transcription, Genetic*
  • Ubiquinone / analogs & derivatives
  • Ubiquinone / metabolism


  • Carrier Proteins
  • RNA, Messenger
  • Ubiquinone
  • Ribonucleases
  • Phosphopyruvate Hydratase
  • Electron Transport Complex III
  • ubiquinol

Associated data

  • GENBANK/U90319
  • GENBANK/U91748