Widespread occurrence of spliceosomal introns in the rDNA genes of ascomycetes.
Journal Article (Journal Article)
Spliceosomal (pre-mRNA) introns have previously been found in eukaryotic protein-coding genes, in the small nuclear RNAs of some fungi, and in the small- and large-subunit ribosomal DNA genes of a limited number of ascomycetes. How the majority of these introns originate remains an open question because few proven cases of recent and pervasive intron origin have been documented. We report here the widespread occurrence of spliceosomal introns (69 introns at 27 different sites) in the small- and large-subunit nuclear-encoded rDNA of lichen-forming and free-living members of the Ascomycota. Our analyses suggest that these spliceosomal introns are of relatively recent origin, i.e., within the Euascomycetes, and have arisen through aberrant reverse-splicing (in trans) of free pre-mRNA introns into rRNAs. The spliceosome itself, and not an external agent (e.g., transposable elements, group II introns), may have given rise to these introns. A nonrandom sequence pattern was found at sites flanking the rRNA spliceosomal introns. This pattern (AG-intron-G) closely resembles the proto-splice site (MAG-intron-R) postulated for intron insertions in pre-mRNA genes. The clustered positions of spliceosomal introns on secondary structures suggest that particular rRNA regions are preferred sites for insertion through reverse-splicing.
Full Text
Duke Authors
Cited Authors
- Bhattacharya, D; Lutzoni, F; Reeb, V; Simon, D; Nason, J; Fernandez, F
Published Date
- December 2000
Published In
Volume / Issue
- 17 / 12
Start / End Page
- 1971 - 1984
PubMed ID
- 11110913
Electronic International Standard Serial Number (EISSN)
- 1537-1719
International Standard Serial Number (ISSN)
- 0737-4038
Digital Object Identifier (DOI)
- 10.1093/oxfordjournals.molbev.a026298
Language
- eng