SL1 TRANSSPLICING SPECIFIED BY AU-RICH SYNTHETIC RNA INSERTED AT THE 5'-END OF CAENORHABDITIS-ELEGANS PRE-MESSENGER-RNA

In Caenorhabditis elegans, pre-mRNAs of many genes are trans-spliced t o one of two spliced leaders, SL1 or SL2. Some of those that receive e xclusively SL1 have been characterized as having at their 5' ends outr ons, AU-rich sequences similar to introns followed by conventional 3' splice sites. Comparison of outrons from many different SL1-specific C . elegans genes has not revealed the presence of any consensus sequenc e that might encode SL1-specificity. In order to determine what parame ters influence the splicing of SL1, we performed in vivo experiments w ith synthetic splice sites. Synthetic AU-rich RNA, 51 nt or longer, pl aced upstream of a consensus 3' splice site resulted in efficient tran s-splicing. With all sequences tested, this trans-splicing was specifi cally to SL1. Thus, no information beyond the presence of AU-rich RNA at least as long as the minimum-length C. elegans intron, followed by a 3' splice site, is required to specify trans-splicing or for strict SL1 specificity.