Abstract
Splicing is an efficient and precise mechanism that removes noncoding regions from a single primary RNA transcript. Cutting and rejoining of the segments occurs on nascent RNA. Trans-splicing between small specialized RNAs and a primary transcript has been known in some organisms but recent papers show that trans-splicing between two RNA molecules containing different coding regions is the normal mode in a Drosophila gene. The mod(mdg4) gene produces 26 different mRNAs encoding as many protein isoforms. The differences lie in alternative 3' exons encoded by different transcriptional units and spliced to the 5' common region by a surprising trans-splicing mechanism.
