Potential movement of transposable elements through DNA circularization

Abstract

The generation of circular DNAs is a relatively unrecognized type of genomic structural variation, but recent findings point to a possible role of circular DNAs in the movement of transposable elements. Circularization of genomic DNA is observed across eukaryotic species, in a range of different cell types, and from all parts of the genome. A recent study on circular DNAs in yeast found that transposable element sequence residing in circular structures mostly corresponded to full-length transposable elements. Transposable elements are mobile genetic elements scattered across eukaryotic genomes. Different classes of transposable elements move either through a copy-and-paste or a cut-and-paste. As circular DNA structures may recombine with the genome and re-integrate into a novel genomic locus, transposable elements could move through circularization. In yeast, the predominant type of transposable element is a so-called LTR (long terminal repeats) retrotransposable element that moves through a copy-and-paste mechanism. The observed circularization of this element means it potentially could move through a cut-and-paste mechanism as well. Although further experimental evidence is needed to establish the extent to which movement of transposable elements through DNA circularization takes place, such movement is likely to have a functional impact on the genomic context.

Diversity of PBI-DdeI satellite DNA in snakes correlates with rapid independent evolution and different functional roles

“…kaouthia . Further study is required to elucidate the molecular mechanisms of PBI-DdeI dispersion in snake lineages, with possibilities including extra-chromosomal circular process DNAs or transposable element arrest processes 35,36 .…”

Small extrachromosomal circular DNA (eccDNA): major functions in evolution and cancer

“…Circular DNAs are produced by cleavage and ligation and can be enlarged by the integration of other DNA components, such as TEs and enhancers/promoters. BFB, breakage-fusion-bridge but findings from other research studies have noted a possible role of circular DNAs in the movement of TEs [51]. The frequency of these elements in cancer cells is higher than that in normal cells, which indicates that these elements might contribute to the instability of the genome.…”

“…This amplification is mediated by small circular DNAs, which are referred to as episomes. An episome is likely an unrecognized type of structural variation in the genome, but findings from other research studies have noted a possible role of circular DNAs in the movement of TEs [ 51 ]. The frequency of these elements in cancer cells is higher than that in normal cells, which indicates that these elements might contribute to the instability of the genome.…”

“…For example, a previous study revealed the eccDNA-based amplification and transmission of herbicide resistance in the crop weed Amaranthus palmeri [ 54 ]. Most retrotransposable elements move through a copy-and-paste or cut-and-paste mechanism, and this movement is likely to have a functional impact on the genomic context [ 51 ]. For example, transposon-like sequences, called telomere-bearing elements (TBEs), in Oxytricha are excised as eccDNA molecules during rearrangement, which results from rejoining to regenerate the target [ 55 ] (Fig.…”

Modulating signaling networks by CRISPR/Cas9-mediated transposable element insertion

“…The transposition mechanism by which TEs are scattered into host genome challenged the mistaken concept that considered the genome as one fixed, immutable entity (Mourier 2016). Nowadays, it is well known that transposition comprises an important adaptive mechanism capable of providing both hereditable and non-hereditable variability, source of critical phenotypic plasticity.…”