Identification of novel small-molecule inhibitors of SARS-CoV-2 by chemical genetics

There are only eight approved small molecule antiviral drugs for treating COVID-19.Among them,four are nucleotide analogues(remdesivir,JT001,molnupiravir,and azvudine),while the other four are protease inhibitors(nirmatrelvir,ensitrelvir,leritrelvir,and simnotrelvir-ritonavir).Antiviral resistance,unfavourable drug‒drug interaction,and toxicity have been reported in previous studies.Thus there is a dearth of new treatment options for SARS-CoV-2.In this work,a three-tier cell-based screening was employed to identify novel compounds with anti-SARS-CoV-2 activity.One compound,designated 172,demonstrated broad-spectrum antiviral activity against multiple human pathogenic coronaviruses and different SARS-CoV-2 variants of concern.Mechanistic studies validated by reverse genetics showed that compound 172 inhibits the 3-chymotrypsin-like protease(3CLpro)by binding to an allosteric site and reduces 3CLpro dimerization.A drug synergistic checkerboard assay demonstrated that compound 172 can achieve drug synergy with nirmatrelvir in vitro.In vivo studies confirmed the antiviral activity of compound 172 in both Golden Syrian Hamsters and K18 humanized ACE2 mice.Overall,this study identified an alternative druggable site on the SARS-CoV-23CLpro,proposed a potential combination therapy with nirmatrelvir to reduce the risk of antiviral resistance and shed light on the development of allosteric protease inhibitors for treating a range of coronavirus diseases.

Identification of Methylosome Components as Negative Regulators of Plant Immunity Using Chemical Genetics

Nucleotide-binding leucine-rich repeat （NLR） proteins serve as immune receptors in both plants and animals. To identify components required for NLR-mediated immunity, we designed and carried out a chemical genetics screen to search for small molecules that can alter immune responses in Arabidopsis thaliana. From 13 600 compounds, we identified Ro 8-4304 that was able to specifically suppress the severe autoimmune phenotypes of chs3-2D （chilling sensitive 3, 2D）, including the arrested growth morphology and heightened PR （Pathogenesis Related） gene expression. Further, six Ro 8-4304 insensitive mutants were uncovered from the Ro 8-4304-insensitive mutant （rim） screen using a mutagenized chs3-2D popula- tion. Positional cloning revealed thatriml encodes an allele of AtlCIn （I, currents; CI, chloride; n, nucleotide）. Genetic and biochemical analysis demonstrated that AtlCIn is in the same protein complex with the meth- ylosome components small nuclear ribonucleoprotein D3b （SmD3b） and protein arginine methyltransferase 5 （PRMT5）, which are required for the biogenesis of small nuclear ribonucleoproteins （snRNPs） involved in mRNA splicing. Double mutant analysis revealed that SmD3b is also involved in the sensitivity to Ro 8-4304, and the prmt5-1 chs3-2D double mutant is lethal. Loss of At/C/n, SmD3b, or PRMT5 function results in enhanced disease resistance against the virulent oomycete pathogen Hyaloperonospora arabidopsidis Noco2, suggesting that mRNA splicing plays a previously unknown negative role in plant immunity. The successful implementation of a high-throughput chemical genetic screen and the identification of a small-molecule compound affecting plant immunity indicate that chemical genetics is a powerful tool to study whole-organism plant defense pathways.

Interplay of phytohormones and epigenetic regulation:A recipe for plant development and plasticity

Both phytohormone signaling and epigenetic mechanisms have long been known to play crucial roles in plant development and plasticity in response to ambient stimuli.Indeed,diverse signaling pathways mediated by phytohormones and epigenetic processes integrate multiple upstream signals to regulate various plant traits.Emerging evidence indicates that phytohormones and epigenetic processes interact at multiple levels.In this review,we summarize the current knowledge of the interplay between phytohormones and epigenetic processes from the perspective of phytohormone biology.We also review chemical regulators used in epigenetic studies and propose strategies for developing novel regulators using multidisciplinary approaches.

An Integrated Systems Biology Approach Identifies ZIKV and DENV Replication

The Zika virus(ZIKV)and dengue virus(DENV)flaviviruses exhibit similar replicative processes but have distinct clinical outcomes.A systematic understanding of virus–host protein–protein interaction networks can reveal cellular pathways critical to viral replication and disease pathogenesis.Here we employed three independent systems biology approaches toward this goal.First,protein array analysis of direct interactions between individual ZIKV/DENV viral proteins and20,240 human proteins revealed multiple conserved cellular pathways and protein complexes,including proteasome complexes.Second,an RNAi screen of 10,415 druggable genes identified the host proteins required for ZIKV infection and uncovered that proteasome proteins were crucial in this process.Third,high-throughput screening of 6016 bioactive compounds for ZIKV inhibition yielded 134 effective compounds,including six proteasome inhibitors that suppress both ZIKV and DENV replication.Integrative analyses of these orthogonal datasets pinpoint proteasomes as critical host machinery for ZIKV/DENV replication.Our study provides multi-omics datasets for further studies of flavivirus–host interactions,disease pathogenesis,and new drug targets.