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Coevolution of group II intron RNA structures with their intron-encoded reverse transcriptases.
N Toor1, G Hausner, S Zimmerly
1Department of Biological Sciences, University of Calgary, Alberta, Canada.
RNA (New York, N.Y.)
|August 11, 2001
Summary
Group II introns evolved alongside their encoded proteins (reverse transcriptases), not as independent catalytic RNAs. This retroelement ancestor hypothesis explains the development of major RNA structures and suggests most ORF-less introns derive from those with ORFs.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- RNA Biology
Background:
- Catalytic RNAs, like group II introns, are considered remnants of the RNA World.
- Understanding the evolutionary history of these molecules, particularly their structures and associated proteins, remains challenging.
Purpose of the Study:
- To investigate the coevolution of group II intron RNA structures and their encoded reverse transcriptases (RTs).
- To propose a new model for the evolution of group II introns.
Main Methods:
- Comparative analysis of group II intron RNA structures and their open reading frames (ORFs).
- Phylogenetic analysis of intron-encoded proteins and RNA secondary structures.
- Examination of the distribution patterns of ORF-containing and ORF-less introns.
Main Results:
- Six classes of group II introns encoding ORFs were identified, with three being conventional (A1, B1, B2) and three being bacterial with unusual or hybrid features.
- No evidence of significant "reshuffling" between intron RNA structures and ORFs was observed, unlike in group I introns.
- ORF-less introns often contain remnants of ORFs, supporting their derivative nature.
Conclusions:
- The retroelement ancestor hypothesis proposes that group II intron major RNA structural forms coevolved with their intron-encoded proteins.
- This model suggests that most ORF-less introns are derived from ORF-containing introns.
- The findings provide insights into the evolutionary pathways of mobile genetic elements and the RNA World.