Comparison of transfer RNA and ribosomal RNA intron splicing in the extreme thermophile and archaebacterium Desulfurococcus mobilis

The structure of the exon–intron boundary was compared for an intron within 23S ribosomal RNA of Desulfurococcus mobilis and a newly discovered intron in tRNAMet from the same organism. The occurrence of a putative common structural feature suggests that intron excision occurs by the same mechanism. The possible recognition of this structural feature by the cleavage enzyme was investigated for the ribosomal RNA intron using RNA substrates exhibiting various exon and intron deletions. The results support the involvement of the structural features in the cleavage process. The evolutionary implications of these results are considered.Key words: archaebacteria, tRNA, ribosomal RNA, introns, intron evolution.