INVIVO PROCESSING OF AN INTRON-CONTAINING ARCHAEL TRANSFER-RNA

In vitro studies on the processing of halobacterial tRNA introns have led to the proposal that archaeal and eukaryotic tRNA intron endonucleases have distinctly different requirements for the recognition of pre-tRNAs. Using a Haloferax volcanii in vivo expression vector we have examined the in vivo processing of modified forms of the halobacterial intron-containing tRNA(Trp) gene. As observed in vitro, changes in the exon-intron boundary structure of this pre-tRNA block processing. Intron sequences, other than those at the exon-intron boundaries, are not essential for processing in vivo. We also show that conversion of the tryptophan anticodon to an opal suppressor anticodon is tolerated when the exon-intron boundary structure is maintained.