Transposable Elements as a Source of Novel Repetitive DNA in the Eukaryote Genome

Abstract

The impact of transposable elements (TEs) on the evolution of the eukaryote genome has been observed in a number of biological processes, such as the recruitment of the host's gene expression network or the rearrangement of genome structure. However, TEs may also provide a substrate for the emergence of novel repetitive elements, which contribute to the generation of new genomic components during the course of the evolutionary process. In this review, we examine published descriptions of TEs that give rise to tandem sequences in an attempt to comprehend the relationship between TEs and the emergence of de novo satellite DNA families in eukaryotic organisms. We evaluated the intragenomic behavior of the TEs, the role of their molecular structure, and the chromosomal distribution of the paralogous copies that generate arrays of repeats as a substrate for the emergence of new repetitive elements in the genome. We highlight the involvement and importance of TEs in the eukaryote genome and its remodeling processes.

Keywords: TE life cycle; centromeric region; satellite DNA; tandem repeats.

Figure 1

Life cycle of a transposable element, using LTR transposons with their respective Open Reading Frames (ORFs) as an example. T0—simple copy of the element in the genome; T1—Invasion: the chromosomal locus acquires at least one repeat unit; T2—Amplification: an increase in the number of copies present in the genome, either by burst events (in the case of class I elements) or the repair or homologous recombination of double-stranded DNA (class II); T3—Maturation: the elements are inactivated or silenced through epigenetic silencing, piRNAs, DNA methylation or other mechanisms, such as mutations; T4—Death or degeneration: the elements may be either eliminated from the genome, undergo molecular domestication, begin to exercise new functions or give rise to new repetitive sequences, such as tandem repeats. LTR = Long Terminal Repeat; ORF = Open Reading Frame. (Source: the authors / created in Biorender.com, accessed on 5 September 2022).

Figure 2

Schematic diagram of the different regions of transposable elements that may provide the starting point of origin for new micro-, mini- or satellite DNA. LTR (Long Terminal Repeat); GAG (GAG domain); POL (Reverse Transcriptase); ENV (Envelope Protein); UTR (Untranslated Region); ORF (Open Reading Frame); TIR (Terminal Inverted Repeats). (Source: the authors/created in Biorender.com, accessed on 5 September 2022).

Figure 3

Schematic diagram showing how the Non-Homologous End-Joining (NHEJ) and Non-Allelic Homologous Recombination (NAHR) DNA repair mechanisms contribute to the expansion of tandem repeats from a Transposable Element. TSD (Target Site Duplication); TIR (Terminal Inverted Repeats); ORF (Open Reading Frame). (Source: Authors/created in Biorender.com, accessed on 5 September 2022).