Foldback intercoil DNA and the mechanism of DNA transposition

The unusual structural properties and potential biological relevance of switchback DNA

Synthetic DNA motifs form the basis of nucleic acid nanotechnology. The biochemical and biophysical properties of these motifs determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

The unusual structural properties and potential biological relevance of switchback DNA

Synthetic DNA motifs form the basis of nucleic acid nanotechnology, and their biochemical and biophysical properties determine their applications. Here, we present a detailed characterization of switchback DNA, a globally left-handed structure composed of two parallel DNA strands. Compared to a conventional duplex, switchback DNA shows lower thermodynamic stability and requires higher magnesium concentration for assembly but exhibits enhanced biostability against some nucleases. Strand competition and strand displacement experiments show that component sequences have an absolute preference for duplex complements instead of their switchback partners. Further, we hypothesize a potential role for switchback DNA as an alternate structure in sequences containing short tandem repeats. Together with small molecule binding experiments and cell studies, our results open new avenues for switchback DNA in biology and nanotechnology.

Transposable elements and their role in aging

Transposable elements (TEs) are an important part of eukaryotic genomes. The role of somatic transposition in aging, carcinogenesis, and other age-related diseases has been determined. This review discusses the fundamental properties of TEs and their complex interactions with cellular processes, which are crucial for understanding the diverse effects of their activity on the genetics and epigenetics of the organism. The interactions of TEs with recombination, replication, repair, and chromosomal regulation; the ability of TEs to maintain a balance between their own activity and repression, the involvement of TEs in the creation of new or alternative genes, the expression of coding/non-coding RNA, and the role in DNA damage and modification of regulatory networks are reviewed. The contribution of the derepressed TEs to age-dependent effects in individual cells/tissues in different organisms was assessed. Conflicting information about TE activity under stress as well as theories of aging mechanisms related to TEs is discussed. On the one hand, transposition activity in response to stressors can lead to organisms acquiring adaptive innovations of great importance for evolution at the population level. On the other hand, the TE expression can cause decreased longevity and stress tolerance at the individual level. The specific features of TE effects on aging processes in germline and soma and the ways of their regulation in cells are highlighted. Recent results considering somatic mutations in normal human and animal tissues are indicated, with the emphasis on their possible functional consequences. In the context of aging, the correlation between somatic TE activation and age-related changes in the number of proteins required for heterochromatin maintenance and longevity regulation was analyzed. One of the original features of this review is a discussion of not only effects based on the TEs insertions and the associated consequences for the germline cell dynamics and somatic genome, but also the differences between transposon- and retrotransposon-mediated structural genome changes and possible phenotypic characteristics associated with aging and various age-related pathologies. Based on the analysis of published data, a hypothesis about the influence of the species-specific features of number, composition, and distribution of TEs on aging dynamics of different animal genomes was formulated.

Effects of ionizing radiation at Drosophila melanogaster with differently active hobo transposons

Purpose: The role of transposable elements in formation of radiobiological effects is understudied and contradictory. The aim of this study was to investigate the response of Drosophila melanogaster to irradiation depending on the level of activity hobo transposons and the role of hobo transposons in formation of ionizing radiation late effects.Materials and methods: The individuals of Drosophila melanogaster with different level activity of hobo-elements were exposed to acute irradiation in doses of 1-100 Gy at early ontogenesis stages. The reaction of individuals to exposure was studied using the larvae survival rate, morphological parameters of reproduction system, DNA damage rate, and mutability of mini-white locus.Results: We found the pronounced linear deferred effects of irradiation for animals with a high activity level of full-size hobo copies. The radiosensitivity of individuals with a mean level of activity transposon was whether higher or did not differ from the radiosensitivity of animals with a low activity hobo.Conclusion: The obtained results suggest that full-size hobo-elements with a high activity level (less often with a mean activity level) are responsible for delayed deleterious irradiation effects.