A naturally occurring non-coding fusion transcript derived from scorpion venom gland: implication for the regulation of scorpion toxin gene expression

Scorpion venom glands synthesize and secrete a great number of low molecula r mass toxic peptides for prey and defense. Many cDNAs and genomic genes en coding these toxins have been isolated and sequenced. However, their expres sion regulation mechanism is not yet known at present. During screening of a cDNA library prepared from venom glands of the scorpion Buthus martensii Karsch, we isolated a natural fusion cDNA composed of the 5'-untranslated r egion (UTR) and upstream coding sequence of a long-chain toxin transcript a nd the downstream coding sequence and 3'-UTR of a short-chain toxin transcr ipt. The junction site is just the overlapping region of 11 nucleotides (GG CAAGGAAAT) between the two wild transcripts, and thus leads to the formatio n of an early stop codon, which will cause premature translation. Based on the above observations, combined with the genomic data, we proposed a chara cteristic regulation mechanism of scorpion toxin genes, in which trans-spli cing and nonsense mediated mRNA decay are involved. (C) 2001 Published by E lsevier Science B.V. on behalf of the Federation of European Biochemical So cieties.