G4-DNA Formation and Chromatin Remodelling are Interdependent in Human Cells [ATAC-seq]

DNA G-quadruplexes (G4s) have been identified as important biological targets for transcriptional, translational, and epigenetic regulation. The stabilisation of G4s with small molecule ligands has emerged as a technique to regulate gene expression and as a potential therapeutic approach for human diseases. Here, we demonstrate that ligand stabilisation of G4s causes altered chromatin accessibility dependant on the targeting specificity of the molecule. In particular, stabilisation of a target G4 using the highly specific GTC365 ligand resulted in differential accessibility of 61 genomic regions, while the broad targeted GQC-05 ligand stabilised many G4s and induced a global shift towards increased accessibility of gene promoter regions. Interestingly, while we observed distinct effects of each ligand on RNA expression levels and the induction of DNA double-stranded breaks, both ligands modified DNA damage response pathways. Our work represents the dual possibility of G4-stabilising ligands for specific or global chromatin modulation via unique targeting characteristics. Overall design: To investigate the potential for G4 stabilisation to alter chromatin organisation and subsequent gene expression, we treated MCF-7 cells with GQC-05 and GTC365 G4-stabilising ligands and then performed ATAC- and RNA-seq.