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Popular articles in MDNA

We are very proud to present some of the articles which were most popular in the field over the last 12 months. The following list consists of a mix of articles that were cited well and articles which created a buzz on social media, upon publication in Mobile DNA.

Paired-end mappability of transposable elements in the human genome
Corinne E. Sexton & Mira V. Han
Mobile DNA 10, 29 (2019)

Though transposable elements make up around half of the human genome, the repetitive nature of their sequences makes it difficult to accurately align conventional sequencing reads. However, in light of new advances in sequencing technology, such as increased read length and paired-end libraries, these repetitive regions are now becoming easier to align to. This study investigates the mappability of transposable elements with 50 bp, 76 bp and 100 bp paired-end read libraries. With respect to those read lengths and allowing for 3 mismatches during alignment, over 68, 85, and 88% of all transposable elements in the RepeatMasker database are uniquely mappable, suggesting that accurate locus-specific mapping of older transposable elements is well within reach.

Differential retention of transposable element-derived sequences in outcrossing Arabidopsis genomes
Sylvain Legrand, Thibault Caron, Florian Maumus, Sol Schvartzman, Leandro Quadrana, Eléonore Durand, Sophie Gallina, Maxime Pauwels, Clément Mazoyer, Lucie Huyghe, Vincent Colot, Marc Hanikenne & Vincent Castric
Mobile DNA 10, 30 (2019)

Transposable elements (TEs) are genomic parasites with major impacts on host genome architecture and host adaptation. A proper evaluation of their evolutionary significance has been hampered by the paucity of short scale phylogenetic comparisons between closely related species. Here, we characterized the dynamics of TE accumulation at the micro-evolutionary scale by comparing two closely related plant species, Arabidopsis lyrata and A. halleri.

Convergence in LINE-1 nucleotide variations can benefit redundantly forming triplexes with lncRNA in mammalian X-chromosome inactivation
Yoko Matsuno, Takefumi Yamashita, Michiru Wagatsuma & Hajime Yamakage
Mobile DNA 10, 33 (2019)

Associations between X-inactive transcript (Xist)–long noncoding RNA (lncRNA) and chromatin are critical intermolecular interactions in the X-chromosome inactivation (XCI) process. Despite high-resolution analyses of the Xist RNA-binding sites, specific interaction sequences are yet to be identified. Based on elusive features of the association between Xist RNA and chromatin and the possible existence of multiple low-affinity binding sites in Xist RNA, we defined short motifs (≥5 nucleotides), termed as redundant UC/TC (r-UC/TC) or AG (r-AG) motifs, which may help in the mediation of triplex formation between the lncRNAs and duplex DNA.

The Transposon Registry
Supathep Tansirichaiya, Md. Ajijur Rahman & Adam P. Roberts
Mobile DNA 10, 40 (2019)

Transposable elements in prokaryotes are found in many forms and therefore a robust nomenclature system is needed in order to allow researchers to describe and search for them in publications and databases. Here we provide an update on The Transposon Registry which allocates numbers to any prokaryotic transposable element. Additionally, we present the completion of registry records for all transposons assigned Tn numbers from Tn1 onwards where sequence data or publications exist.

LTR_FINDER_parallel: parallelization of LTR_FINDER enabling rapid identification of long terminal repeat retrotransposons
Shujun Ou & Ning Jiang
Mobile DNA 10, 48 (2019)

Annotation of plant genomes is still a challenging task due to the abundance of repetitive sequences, especially long terminal repeat (LTR) retrotransposons. LTR_FINDER is a widely used program for the identification of LTR retrotransposons but its application on large genomes is hindered by its single-threaded processes. Here we report an accessory program that allows parallel operation of LTR_FINDER, resulting in up to 8500X faster identification of LTR elements. It takes only 72 min to process the 14.5 Gb bread wheat (Triticum aestivum) genome in comparison to 1.16 years required by the original sequential version.

Integrating transposable elements in the 3D genome
Alexandros Bousios, Hans-Wilhelm Nützmann, Dorothy Buck & Davide Michieletto
Mobile DNA 11, 8 (2020)

Chromosome organisation is increasingly recognised as an essential component of genome regulation, cell fate and cell health. Within the realm of transposable elements (TEs) however, the spatial information of how genomes are folded is still only rarely integrated in experimental studies or accounted for in modelling. Whilst polymer physics is recognised as an important tool to understand the mechanisms of genome folding, in this commentary we discuss its potential applicability to aspects of TE biology. Based on recent works on the relationship between genome organisation and TE integration, we argue that existing polymer models may be extended to create a predictive framework for the study of TE integration patterns. We suggest that these models may offer orthogonal and generic insights into the integration profiles (or “topography”) of TEs across organisms. In addition, we provide simple polymer physics arguments and preliminary molecular dynamics simulations of TEs inserting into heterogeneously flexible polymers. By considering this simple model, we show how polymer folding and local flexibility may generically affect TE integration patterns. The preliminary discussion reported in this commentary is aimed to lay the foundations for a large-scale analysis of TE integration dynamics and topography as a function of the three-dimensional host genome.

Hybrid dysgenesis in Drosophila virilis results in clusters of mitotic recombination and loss-of-heterozygosity but leaves meiotic recombination unaltered
Lucas W. Hemmer, Guilherme B. Dias, Brittny Smith, Kelley Van Vaerenberghe, Ashley Howard, Casey M. Bergman & Justin P. Blumenstiel
Mobile DNA 11, 10 (2020)

Transposable elements (TEs) are endogenous mutagens and their harmful effects are especially evident in syndromes of hybrid dysgenesis. In Drosophila virilis, hybrid dysgenesis is a syndrome of incomplete gonadal atrophy that occurs when males with multiple active TE families fertilize females that lack active copies of the same families. This has been demonstrated to cause the transposition of paternally inherited TE families, with gonadal atrophy driven by the death of germline stem cells. Because there are abundant, active TEs in the male inducer genome, that are not present in the female reactive genome, the D. virilis syndrome serves as an excellent model for understanding the effects of hybridization between individuals with asymmetric TE profiles.

Hagfish genome reveals parallel evolution of 7SL RNA-derived SINEs
Kenji K. Kojima
Mobile DNA 11, 18 (2020)

Short interspersed elements (SINEs) are ubiquitous components of eukaryotic genomes. SINEs are composite transposable elements that are mobilized by non-long terminal repeat (non-LTR) retrotransposons, also called long interspersed elements (LINEs). The 3′ part of SINEs usually originated from that of counterpart non-LTR retrotransposons. The 5′ part of SINEs mostly originated from small RNA genes. SINE1 is a group of SINEs whose 5′ part originated from 7SL RNA, and is represented by primate Alu and murine B1. Well-defined SINE1 has been found only from Euarchontoglires, a group of mammals, in contrast to the wide distribution of SINE2, which has a tRNA-derived sequence, from animals to plants to protists. Both Alu and B1 are mobilized by L1-type non-LTR retrotransposons, which are the only lineage of autonomous non-LTR retrotransposons active in these mammalian lineages.