Transposable elements: a comparative study in the introns and UTRs of the homologous mitochondrial solute carrier genes of Human, Mouse and Zebrafish

We studied the localization of transposable elements (TEs) in the 5’ and 3’ flanking regions and in the introns of Mouse, Human and Zebrafish mitochondrial solute carrier genes. The canonical transcripts of these highly homologous genes exhibit superimposable patterns of exon-intron alternation in the three species. In introns, two sections approximately corresponding to the first and last 20 nucleotides are relatively, but not completely, depleted of TEs. The distributions of the distances of the TEs which are the closer to the start and stop codons are right-skewed, with lower values for short distances, a peak at 750 nt in Mouse and Human and 450 nt in Zebrafish, followed by an exponential decay. Taken together these results suggest that the exon/ intron structuring of the mitochondrial solute carrier genes has been under strict evolutionary control from fish to mammals and variants with potentially dangerous inserts (such as LTR elements) nearing the regulatory sequences have been selected against, whilst the extant TEs do not exert any significant action not even at relatively short distances. Keywords: Mitochondrial solute carrier genes; Transposable elements; UTRs; Introns; Human; Mouse; Zebrafish