Stress promotes RNA G-quadruplex folding in human cells

Guanine-rich nucleic acids can fold into G-quadruplex (G4) structures. Although endogenous RNAs contain sequences that can fold into RNA G4s (rG4s) in vitro, their folding and functions in vivo are not well understood. We show that the folding of putative rG4s in human cells into bona fide rG4 structures is dynamically regulated by stress. By using a high-throughput approach based on differential reactivity of dimethyl sulfate (DMS) towards Gs within folded vs unfolded rG4s, we identified hundreds of endogenous rG4s whose folding is promoted by cellular stress and validated them using a newly developed rG4-specific ligand. Stress-dependent rG4s are enriched in mRNA 3'-untranslated regions, suggesting their role in regulating mRNA stability under stress. Lastly, rG4 folding is reversible upon stress removal or adaptation. Our study show that rG4s function as regulatory elements in regulating mRNA stability and cellular stress response. One-Sentence SummaryRNA G-quadruplexes assemble under stress in human cells