DNA G-quadruplex structures: more than simple roadblocks to transcription?

Abstract It has been >20 years since the formation of G-quadruplex (G4) secondary structures in gene promoters was first linked to the regulation of gene expression. Since then, the development of small molecules to selectively target G4s and their cellular application have contributed to an improved understanding of how G4s regulate transcription. One model that arose from this work placed these non-canonical DNA structures as repressors of transcription by preventing polymerase processivity. Although a considerable number of studies have recently provided sufficient evidence to reconsider this simplistic model, there is still a misrepresentation of G4s as transcriptional roadblocks. In this review, we will challenge this model depicting G4s as simple ‘off switches’ for gene expression by articulating how their formation has the potential to alter gene expression at many different levels, acting as a key regulatory element perturbing the nature of epigenetic marks and chromatin architecture. Graphical Abstract Graphical Abstract DNA G-quadruplexes act as transcriptional hubs by means of diverse mechanisms, including: modulation of chromatin structure, regulatory protein recruitment and formation of DNA loops, stimulation of liquid-liquid phase separation and eliciting DNA damage and repair.