ALTERNATIVE SPLICING IN THE CAENORHABDITIS-ELEGANS DNA TOPOISOMERASE-I GENE

5'-end cDNA fragments of the Caenorhabditis elegans DNA topoisomerase I gene were obtained by rapid amplification of the cDNA ends from C. e legans mRNAs. The presence of a SL1 sequence at the 5'-terminus of the cDNA sequence suggested trans-splicing of the pre-mRNA. By comparing the complete cDNA sequence with the genomic lambda DNA clones, the gen e structure composed of five exons was established. Alternative splici ng deleting the second exon was observed in the cDNA fragments obtaine d by a gene-specific reverse transcription followed by polymerase chai n reactions. The shorter mRNA missing the second exon was expressed at all the developmental stages, while the full-length mRNA was present only in embryos. (C) 1998 Elsevier Science B.V.