Noncanonical DNA structures are drivers of genome evolution

Non-B DNA promotes genomic instability and large-scale rearrangements.In some genomic regions (e.g., promoters and enhancers), G-quadruplex (G4) motifs evolve under purifying selection because of their functionality, yet in some other genomic regions (e.g., coding exons), they might be selected against because of their detrimental effects.Non-B DNA is over-represented in transposable elements (TEs), participates in the life cycle of some of them, and can affect their integration.Many eukaryotic centromeres are specified by non-B DNA.Elevated mutagenicity of non-B DNA may explain some instances of repeated evolution and trans-species polymorphism in fishes and is likely to contribute to phenotypic evolution in other species.