title: Origin of spliceosomal introns and alternative splicing.
abstract: In this work we review the current knowledge on the prehistory, origins, and evolution of spliceosomal introns. First, we briefly outline the major features of the different types of introns, with particular emphasis on the nonspliceosomal self-splicing group II introns, which are widely thought to be the ancestors of spliceosomal introns. Next, we discuss the main scenarios proposed for the origin and proliferation of spliceosomal introns, an event intimately linked to eukaryogenesis. We then summarize the evidence that suggests that the last eukaryotic common ancestor (LECA) had remarkably high intron densities and many associated characteristics resembling modern intron-rich genomes. From this intron-rich LECA, the different eukaryotic lineages have taken very distinct evolutionary paths leading to profoundly diverged modern genome structures. Finally, we discuss the origins of alternative splicing and the qualitative differences in alternative splicing forms and functions across lineages.
authors.affiliation: The Donnelly Centre, University of Toronto, Toronto, Ontario M5S3E1, Canada.
authors.forename: Manuel
authors.initials: M
authors.lastname: Irimia
authors.affiliation: Department of Biology, San Francisco State University, San Francisco, California 94132.
authors.forename: Scott William
authors.initials: SW
authors.lastname: Roy
mesh_terms: D017398:Alternative Splicing; D005091:Exons; D007438:Introns; D017381:Spliceosomes