Group II introns

F. Martinez-Abarca, S. Zekri, and N. Toro, Characterization and in vivo of a Sinorhi-zobium meliloti group II intron associated with particular insertion sequences of the IS630-Tcl/IS3 retroposon superfamily. Mol. Microbiol. 28 1295-1306 (1998). 

Pyle AM (1996) Catalytic reaction mechanisms and structural features of group II intron ribozymes, p 75-107. In Eckstein F, Lilley DMJ (ed) Catalytic RNA, vol 10 Springer, Berlin Heidelberg New York... 

In the reactions, it is likely that Mg ions work as a Lewis acid catalyst to stabilize the leaving oxygens. This stabilization is the same as for group I II and possibly hammerhead ribozymes. But identification of the activator, encouragement of deprotonation of 2 -OH of nucleophiles, remains unclear in the reactions catalyzed by this sn RNA and group II intron ribozymes. 

Figure 4. Transesterification reaction mechanism of group II introns. Nucleophilic attack leads to the pentavalent phosphorus intermediate which subsequently decomposes to yield the cleavage products.

In group II introns the reaction pattern is similar except for the nucleophile in the first step, which in this case is the 2 -hydroxyl group of an A residue within the intron (Fig. 26-15). A branched lariat structure is formed as an intermediate. 

FIGURE 26-15 Splicing mechanism of group II introns. The chemistry is similar to that of group I intron splicing, except for the identity of the nucleophile in the first step and formation of a lariatlike intermediate, in which one branch is a 2, 5 -phosphodiester bond. 

Curcio, M.J. Belfort, M. (1996) Retrohoming cDNA-mediated mobility of group II introns requires a catalytic RNA. Cell 84, 9-12. 

Nonviral methods for DNA incorporation into the human genome may utilize transposons (Chapter 27)166a or mobile group II introns (Chapter 28).166b/C... 

Excision of a group I intron to form a circular RNA and a small oligonucleotide. (B) Excision of a group II intron from yeast mitochondrial pre-mRNA as a circular RNA. See Cech and Bass.581... 

There are six ribozymes that have been successfully modified and/or adapted for use in therapeutic and functional genomic applications. These are the group I introns, RNAse P, the hammerhead and hairpin motifs, the hepatitis delta ribozyme and the reverse splicing reaction of group II introns. Each of these ribozymes requires a divalent metal cation for activity (usually Mg++), which may participate in the chemistry of the cleavage/ligation reaction and/or may be important for maintaining the structure of the ribozyme. 

Guo, H., Karberg, M., Long, M., Jones III, J.P., Sullenger, B. and Lambowitz, A.M. (2000) Group II introns designed to insert into therapeutically relevant DNA target sites in human cells. Science, 289,452—457. 

Single-molecule FRET has been applied to the folding of the group I intron ribozyme (Lee et al, 2007a Russell et al, 2002 Zhuang et al, 2000), the group II intron ribozyme (Steiner et al., 2008), the VS ribozyme (Pereira et al, 2008), and the interaction of a tetraloop and its receptor (Hodak et al.,... 

V of group II introns, some of which are self-spliced via the two-step tran -esterification pathway identical to that of spliceosome-catalyzed pre-mRNA splicing (see above). Domain... 

V of group II introns constitutes the catalytic center for catalysis during self-splicing (129-131). 

Jarrell KA, Dietrich RC, Perlman PS. Group II intron domain 5 facilitates a trans-splicing reaction. Mol. Cell Biol. 1988 8 2361-2366. 

Koch JL, Boulanger SC, Dib-Hajj SD, Hebbar SK, Perlman PS. Group II introns deleted for multiple substructures retain self-splicing activity. Mol. Cell Biol. 1992 12 1950-1958. Michel F, Umesono K, Ozeki H. Comparative and functional anatomy of group II catalytic introns—a review. Gene 1989 82 5-30. 

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