Archaeal introns: splicing, intercellular mobility and evolution.

Until recently, it appeared that archaeal introns were spliced by a process specific to the archaeal domain in which an endoribonuclease cuts a 'bulge-helix-bulge' motif that forms at exon-intron junctions. Recent results, however, have shown that the endoribonuclease involved in archaeal intron splicing is a homologue of two subunits of the enzyme complex that excises eukaryotic nuclear tRNA introns. Moreover, some archaeal introns encode homing enzymes that are also encoded by group I introns.