The COVID-19 pandemic caused by SARS-CoV-2 has become ag lobal threat. Understanding the underlying mechanisms and developing innovativet reatments are extremely urgent. G-quadruplexes (G4s) are important noncanonical nucleic acid structures with distinct biofunctions. Four putative G4-forming sequences (PQSs) in the SARS-CoV-2 genome were studied. One of them (RG-1), which locates in the coding sequence region of SARS-CoV-2 nucleocapsid phosphoprotein (N), has been verified to form astable RNAG4structure in live cells.G4-specific compounds,such as PDP (pyridostatin derivative), can stabilize RG-1 G4 and significantly reduce the protein levels of SARS-CoV-2 Nb y inhibiting its translation both in vitro and in vivo.This result is the first evidence that PQSs in SARS-CoV-2 can form G4 structures in live cells,a nd that their biofunctions can be regulated by aG4-specific stabilizer.This finding will provide new insights into developing novel antiviral drugs against COVID-19.

Both human telomeric G-rich and C-rich DnA have been considered as specific drug targets for cancer therapy. However, due to i-motif structure instability and lack of specific binding agents, it remains unclear whether stabilization of telomeric i-motif can inhibit telomerase activity. single-walled carbon nanotubes (sWnTs) have been reported as the first ligand that can selectively stabilize human telomeric i-motif DnA. Here we report that sWnTs can inhibit telomerase activity through stabilization of i-motif structure. The persistence of i-motif and the concomitant G-quadruplex eventually leads to telomere uncapping and displaces telomerebinding proteins from telomere. The dysfunctional telomere triggers DnA damage response and elicits upregulation of p16 and p21 proteins. This is the first example that sWnTs can inhibit telomerase activity and interfere with the telomere functions in cancer cells. These results provide new insights into understanding the biomedical effects of sWnTs and the biological importance of i-motif DnA.

Long human telomeric fragments can form stable, higher-order G-quadruplex structures, recently identified in human cells, which are potential drug targets. However, there are very few examples of ligand binding to higher-order G-quadruplexes, and all the reported ligands are proposed to bind at the cleft between two G-quadruplexes. Here we report that zinc-finger-like chiral supramolecular complexes prefer binding to higher-order G-quadruplexes over a single G-quadruplex, with ∼200-fold higher selectivity. To our knowledge, this is the first example of a ligand that can distinguish higher-order G-quadruplexes from a single G-quadruplex with such high selectivity. Further studies indicate that the nanosized chiral complex would bind to two well-matched G-quadruplex units, instead of binding at the cleft between the two G-quadruplexes. These results provide new insights into the targeting of higher-order G-quadruplex ligands. Our work illustrates that dimeric G-quadruplex units can be ligand-preferred binding sites.