Evolution of Exons and the Exon–Intron Structure of Long Intergenic Noncoding RNA Genes in Placental Mammals

Abstract

Long intergenic noncoding RNA (lincRNA) genes are abundant in mammals, but their functions remain elusive. The characteristics of lincRNAs can be studied via comparative analysis with those of mRNAs, for which there is a wealth of information. Highly conserved coding sequences (exons) and the exon–intron structure are some typical evolutionary features attributed to eukaryotic mRNAs. The exon structure is conserved considerably less in lincRNA, but to a greater degree than for introns. Comparative analysis of putative intron positions in lincRNA genes in a range of mammalian genomes underscored the high positional conservation for some introns, which appear to be up to 100 million years old. It is therefore possible that primary and/or secondary structure of these molecules confers functional signals.