Selfsplice

Self-splice refers to the self-catalyzed removal of certain RNA introns from transcripts, without the need for proteins. This phenomenon is primarily observed in self-splicing introns, which are ribozymes capable of catalyzing their own excision from RNA precursors. The process yields ligated exons and a separate intron fragment, typically in the form of a lariat or linear RNA, depending on the intron class and context.

There are two main classes of self-splicing introns: group I and group II. Group I introns initiate splicing with the help of an external guanosine cofactor, whose 3' hydroxyl attacks the 5' splice site to generate the first intermediate, followed by a second transesterification that ligates the exons. Group II introns splice via two internal transesterifications that form a 2',5' lariat linkage at the branch point; the second step joins the exons and releases the intron as a lariat. Group II introns often require maturase proteins in vivo, but can fold into active structures in vitro. Both groups can perform cis-splicing within a single RNA molecule or, less commonly, trans-splicing when split across transcripts.

Distribution and significance vary by organism. Self-splicing introns are abundant in organellar genomes (mitochondria and chloroplasts) of plants, fungi, and algae, and are present in some bacteria and archaea. They are of interest for understanding RNA catalysis, evolution (as potential precursors to spliceosomal introns), and biotechnology. In practical terms, self-splicing introns have been explored as tools for genome engineering, gene regulation studies, and the development of ribozyme-based technologies.