IN-VIVO FUNCTION OF MUTATED SPLICED LEADER RNAS IN CAENORHABDITIS-ELEGANS

The role of spliced leader RNA (SL RNA) in trans-splicing in Caenorhab ditis elegans has been studied through a combination of in vitro mutag enesis and in vivo complementation of rrs-1 mutant nematodes, which la ck endogenous SL1 RNA. Three classes of mutant SL1 RNAs have been foun d-those that rescue the lethal phenotype at low concentration of trans forming DNA, those that rescue at high but not low concentration, and those that do not rescue at all. These studies showed that some mutati ons in the otherwise highly conserved 22-nt spliced leader are tolerat ed for splicing and post-splicing events. A longer spliced leader also can be tolerated but only when present in high copy number. Changes i n the first 16 nucleotides result in the appearance of no SL RNA, cons istent with the in vitro studies by others showing that the SL1 RNA pr omoter partly resides within the spliced leader sequence.