A second trans-spliced RNA leader sequence in the nematode Caenorhabditis elegans.

In the nematode Caenorhabditis elegans, the 22-nucleotide RNA sequence called the spliced leader (SL) is trans-spliced from the 100-nucleotide-long SL RNA to some mRNAs. We have identified a trans-spliced leader (SL2) whose sequence differs from that of the original spliced leader (SL1), although both are 22 nucleotides long. By primer-extension sequencing, SL2 but not SL1 was shown to be present at the 5' end of the mRNA encoded by one of the four glyceraldehyde-3-phosphate dehydrogenase genes. The other three glyceraldehyde-3-phosphate dehydrogenase genes encode mRNAs that have the SL1 but not the SL2 sequence at their 5' ends. Therefore, the trans-splicing process can discriminate the transfer of SL1 from that of SL2 in a gene-specific manner.