Structural switches: intracellular G-quadruplexes modulate DNA repair and genome maintenance in <i>Deinococcus radiodurans</i>

Guanine quadruplexes (G4s) can act as both activators and inhibitors of various cellular functions, depending on their genomic position. While G4 functions are increasingly understood in eukaryotes, their specific roles in bacteria, especially <i>in vivo</i>, are still largely unexplored. <i>Deinococcus radiodurans</i> harbors a GC-rich genome with numerous potential G-quadruplex-forming sequences. In this study, the first direct evidence of G4 formation <i>in vivo</i> and its dynamic nature during the DNA damage response to gamma radiation is shown in a bacterium. The significance of G4 structural dynamics in modulating endogenous gene expression, DNA repair, and genome maintenance processes is demonstrated. These findings provide a novel insight into G4-mediated regulatory mechanisms in prokaryotes and expand our understanding of G4's role as a dynamic structural switch.