An early evolutionary origin for the minor spliceosome

• Published in: Nature 2006-10, Vol.443 (7113), p.863-866
• Main Authors: Gray, Michael W, Russell, Anthony G, Charette, J. Michael, Spencer, David F
• Format: Article
• Language: English
• Subjects: Acanthamoeba castellanii - chemistry; Acanthamoeba castellanii - genetics; Animals; Base Sequence; Biological and medical sciences; Catalysis; Eukaryotes; Eukaryotic Cells - metabolism; Evolution, Molecular; Evolutionary biology; Expressed Sequence Tags; Fundamental and applied biological sciences. Psychology; Fungi; Genomics; Humanities and Social Sciences; Humans; Introns - genetics; letter; Microbiology; Molecular and cellular biology; Molecular genetics; Molecular Sequence Data; multidisciplinary; Phylogeny; Proteins; Rhizopus - chemistry; Rhizopus - genetics; Rhizopus oryzae; Ribonucleic acid; RNA; RNA Splicing; RNA, Small Nuclear - genetics; RNA, Small Nuclear - metabolism; Science; Science (multidisciplinary); Spliceosomes - chemistry; Spliceosomes - genetics; Spliceosomes - metabolism; Transcription. Transcription factor. Splicing. Rna processing
• ISSN: 0028-0836; 1476-4687; 1476-4679
• DOI: 10.1038/nature05228

The minor spliceosome is a ribonucleoprotein complex that catalyses the removal of an atypical class of spliceosomal introns (U12-type) from eukaryotic messenger RNAs. It was first identified and characterized in animals, where it was found to contain several unique RNA constituents that share structural similarity with and seem to be functionally analogous to the small nuclear RNAs (snRNAs) contained in the major spliceosome. Subsequently, minor spliceosomal components and U12-type introns have been found in plants but not in fungi. Unlike that of the major spliceosome, which arose early in the eukaryotic lineage, the evolutionary history of the minor spliceosome is unclear because there is evidence of it in so few organisms. Here we report the identification of homologues of minor-spliceosome-specific proteins and snRNAs, and U12-type introns, in distantly related eukaryotic microbes (protists) and in a fungus (Rhizopus oryzae). Cumulatively, our results indicate that the minor spliceosome had an early origin: several of its characteristic constituents are present in representative organisms from all eukaryotic supergroups for which there is any substantial genome sequence information. In addition, our results reveal marked evolutionary conservation of functionally important sequence elements contained within U12-type introns and snRNAs.