1. Modeling G4s in chromatin context confirms partial nucleosome exclusion and reveals nucleosome-disrupting effects of the least selective G4 ligands.
- Author
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Pavlova I, Barinov N, Novikov R, Severov V, Iudin M, Vedekhina T, Larin A, Babenko V, Aralov A, Gnuchikh E, Sardushkin M, Klinov D, Tsvetkov V, and Varizhuk A
- Subjects
- Nucleosomes, Ligands, DNA chemistry, Chromatin genetics, G-Quadruplexes
- Abstract
G-quadruplexes (G4s) are gaining increasing attention as possible regulators of chromatin packaging, and robust approaches to their studies in pseudo-native context are much needed. Here, we designed a simple in vitro model of G4-prone genomic DNA and employed it to elucidate the impact of G4s and G4-stabilizing ligands on nucleosome occupancy. We obtained two 226-bp dsDNA constructs composed of the strong nucleosome positioning sequence and an internucleosomal DNA-imitating tail. The tail was G4-free in the control construct and harbored a "strong" (stable) G4 motif in the construct of interest. An additional "weak" (semi-stable) G4 motif was found within the canonical nucleosome positioning sequence. Both G4s were confirmed by optical methods and
1 H NMR spectroscopy. Electrophoretic mobility assays showed that the weak G4 motif did not obstruct nucleosome assembly, while the strong G4 motif in the tail sequence diminished nucleosome yield. Atomic force microscopy data and molecular modeling confirmed that the strong G4 was maintained in the tail of the correctly assembled nucleosome structure. Using both in vitro and in silico models, we probed three known G4 ligands and detected nucleosome-disrupting effects of the least selective ligand. Our results are in line with the negative correlation between stable G4s and nucleosome density, support G4 tolerance between regularly positioned nucleosomes, and highlight the importance of considering chromatin context when targeting genomic G4s., Competing Interests: Declaration of competing interest All authors have participated in (a) conception and design, or analysis and interpretation of the data; (b) drafting the article or revising it critically for important intellectual content; and (c) approval of the final version. This manuscript has not been submitted to, nor is under review at, another journal or other publishing venue. The authors have no affiliation with any organization with a direct or indirect financial interest in the subject matter discussed in the manuscript., (Copyright © 2022 Elsevier B.V. and Société Française de Biochimie et Biologie Moléculaire (SFBBM). All rights reserved.)- Published
- 2023
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