Kurkin, A. | Search bioRxiv

bioRxiv2022

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

molecular biology↗

bioRxiv2021

Discovery of highly potent pancoronavirus fusion inhibitors that also effectively inhibit COVID-19 variants from the UK and South Africa

We report here the discovery of several highly potent small molecules that showed low nM potency against SARS-CoV (IC50: as low as 13 nM), SARS-CoV-2 (IC50: as low as 23 nM), and MERS-CoV (IC50: as low as 76 nM) in pseudovirus based assays with excellent selectivity indices (SI: as high as > 5000) demonstrating their pancoronavirus inhibition. Some compounds also show 100% inhibition of CPE (IC100) at 1.25 {micro}M against an authentic SARS-CoV-2 (US_WA-1/2020). Furthermore, the most active inhibitors also potently inhibited variants of concerns (VOCs), such as the UK (B.1.1.7), South Africa (B.1.351), and Delta variant (B.1.617.2), originated in India. We confirmed that one of the potent inhibitors binds to the prefusion spike protein trimer of SARS-CoV-2 by SPR. Besides, we showed that they inhibit virus-mediated cell-cell fusion. The ADME data of one of the most active inhibitors, NBCoV1, show drug-like properties. In vivo PK of NBCoV1 in rats demonstrated excellent half-life (t1/2) of 11.3 h, mean resident time (MRT) of 14.2 h, and oral bioavailability. We expect the lead inhibitors to pave the way for further development to preclinical and clinical candidates.

pharmacology and toxicology↗