Premium
Group II intron ribozymes: RNA machines that shape eukaryotic evolution
Author(s) -
Pyle Anna Marie
Publication year - 2007
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.21.5.a41-b
Subject(s) - intron , group ii intron , rna splicing , ribozyme , group i catalytic intron , minor spliceosome , biology , splicing factor , rna , genetics , gene
Group II introns are found primarily in the organellar genes of plants, fungi and yeast, and they also occur in many bacteria. As in nuclear splicing, group II introns are released from precursor RNA as branched lariat molecules, resulting from 5′‐splice site attack by a bulged adenosine within intron. However, unlike nuclear splicing, the catalytic components responsible for this reaction reside within the intron itself. The architectural organization of these components, their pathway for folding, and their role in catalysis by the intron are major areas of work in our laboratory. Group II introns catalyze a remarkable diversity of reactions during self‐splicing and in the process of intron mobility. The first step of splicing is a transesterification reaction that is in constant competition with an alternative hydrolytic pathway for splicing. Although branching is often favored, water readily reacts as the nucleophile during the first step of splicing both in‐vitro and in‐vivo. The two steps of splicing are often highly reversible, explaining the fact that free group II introns can catalyze the facile mobility of group II intron lariats into both RNA and DNA. These reactions are often facilitated by intron‐encoded and nuclear‐encoded proteins in‐vivo, which often serve to stabilize intron conformation and/or contribute to stages of intron mobility. The evolutionary history of group II introns has played a major role in the development of diverse mechanisms for eukaryotic gene expression. It is commonly believed that group II introns served as the evolutionary predecessors of nuclear introns, the eukaryotic splicing apparatus, certain retrotransposons and telomerase. If these hypotheses are even partially correct, then one‐third to one‐half of the human genome has descended from group II introns. And yet their importance is not merely historical, as group II introns continue to have a major influence on the metabolism and genomic stability of modern organisms.