Abstract
BackgroundEukaryotic protein-coding genes consist of exons and introns. Exon–intron borders are conserved between species and thus their changes might be observed only on quite long evolutionary distances. One of the rarest types of change, in which intron relocates over a short distance, is called "intron sliding", but the reality of this event has been debated for a long time. The main idea of a search for intron sliding is to use the most accurate genome annotation and genome sequence, as well as high-quality transcriptome data. We applied them in a search for sliding introns in mammals in order to widen knowledge about the presence or absence of such phenomena in this group.ResultsWe didn’t find any significant evidence of intron sliding in the primate group (human, chimpanzee, rhesus macaque, crab-eating macaque, green monkey, marmoset). Only one possible intron sliding event supported by a set of high quality transcriptomes was observed between EIF1AX human and sheep gene orthologs. Also, we checked a list of previously observed intron sliding events in mammals and showed that most likely they are artifacts of genome annotations and are not shown in subsequent annotation versions as well as are not supported by transcriptomic data.ConclusionsWe assume that intron sliding is indeed a very rare evolutionary event if it exists at all. Every case of intron sliding needs a lot of supportive data for detection and confirmation.
Highlights
Eukaryotic protein-coding genes consist of exons and introns
Out of 35 detected cases only 30 were unique, as we found the same change of the exon–intron boundaries in human SSPO transcript relative to its homologues in mouse Mus musculus, rat Rattus norvegicus, cat Felis catus, dog Canis familiaris, cow Bos taurus, and pig Sus scrofa, suggesting that intron sliding happened in the human lineage
In this study we were searching for intron sliding events in mammals in order to understand the presence or absence of such events in this group
Summary
Eukaryotic protein-coding genes consist of exons and introns. Exon–intron borders are conserved between species and their changes might be observed only on quite long evolutionary distances. Eukaryotic genes consist of exons and introns whose borders, i.e. genomic coordinates, are evolutionarily conservative which means they are under the pressure of negative selection [1,2,3,4]. The changes of exon–intron boundaries might affect coding protein, they are rare events and can be seen only on the long evolutionary distances [5]. Such changes differ from the alternative splicing, which is widespread in eukaryotes and does not affect exon–intron coordinates. The longer the distance is, the more sceptical we might be about the presence of an intron sliding event rather than intron loss and gain in different positions
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