Biology subjects

Xiong, W.

Publications and source records attributed to Xiong, W..

At least 37 records · Page 2Linked to original sources

bioRxiv2023

Human Surfactant Protein A Alleviates SARS-CoV-2 Infectivity in Human Lung Epithelial Cells

SARS coronavirus 2 (SARS-CoV-2) infects human angiotensin-converting enzyme 2 (hACE2)-expressing lung epithelial cells through its spike (S) protein. The S protein is highly glycosylated and could be a target for lectins. Surfactant protein A (SP-A) is a collagen-containing C-type lectin, expressed by mucosal epithelial cells and mediates its antiviral activities by binding to viral glycoproteins. This study examined the mechanistic role of human SP-A in SARS-CoV-2 infectivity. The interactions between human SP-A and SARS-CoV-2 S protein and hACE2 receptor, and SP-A level in COVID-19 patients were assessed by ELISA. The effect of SP-A on SARS-CoV-2 infectivity was analyzed by infecting human lung epithelial cells (A549-ACE2) with pseudoviral particles and infectious SARS-CoV-2 (Delta variant) pre-incubated with SP-A. Virus binding, entry, and infectivity were assessed by RT-qPCR, immunoblotting, and plaque assay. The results showed that human SP-A can bind SARS-CoV-2 S protein/RBD and hACE2 in a dose-dependent manner (p<0.01). Human SP-A inhibited virus binding and entry, and reduce viral load in lung epithelial cells, evidenced by the dose-dependent decrease in viral RNA, nucleocapsid protein, and titer (p<0.01). Increased SP-A level was observed in the saliva of COVID-19 patients compared to healthy controls (p<0.05), but severe COVID-19 patients had relatively lower SP-A levels than moderate COVID-19 patients (p<0.05). Therefore, SP-A plays an important role in mucosal innate immunity against SARS-CoV-2 infectivity by directly binding to the S protein and inhibiting its infectivity in host cells. SP-A level in the saliva of COVID-19 patients might serve as a biomarker for COVID-19 severity.

molecular biology↗

bioRxiv2023

TFEB-vacuolar ATPase signaling regulates lysosomal function and microglial activation in tauopathy

Transcription factor EB (TFEB) mediates gene expression through binding to the Coordinated Lysosome Expression And Regulation (CLEAR) sequence. TFEB targets include subunits of the vacuolar ATPase (v-ATPase) essential for lysosome acidification. Single nucleus RNA-sequencing (snRNA-seq) of wild-type and PS19 (Tau) transgenic mice identified three unique microglia subclusters in Tau mice that were associated with heightened lysosome and immune pathway genes. To explore the lysosome-immune relationship, we specifically disrupted the TFEB-v-ATPase signaling by creating a knock-in mouse line in which the CLEAR sequence of one of the v-ATPase subunits, Atp6v1h, was mutated. We show that the CLEAR mutant exhibited a muted response to TFEB, resulting in impaired lysosomal acidification and activity. Crossing the CLEAR mutant with Tau mice led to higher tau pathology but diminished microglia response. These microglia were enriched in a subcluster low in mTOR and HIF-1 pathways and was locked in a homeostatic state. Our studies demonstrate a physiological function of TFEB-v-ATPase signaling in maintaining lysosomal homoeostasis and a critical role of the lysosome in mounting a microglia and immune response in tauopathy and Alzheimers disease.

neuroscience↗

bioRxiv2022

The genome of Lactuca saligna, a wild relative of lettuce, provides insight into non-host resistance to the downy mildew Bremia lactucae

Lactuca saligna L. is a wild relative of cultivated lettuce (Lactuca sativa L.), with which it is partially interfertile. Hybrid progeny suffer from hybrid incompatibilities (HI), resulting in reduced fertility and distorted transmission ratios. Lactuca saligna displays broad spectrum resistance against lettuce downy mildew caused by Bremia lactucae Regel and is considered a non-host species. This phenomenon of resistance in L. saligna is called non-host resistance (NHR). One possible mechanism behind this NHR is through the plant-pathogen interaction triggered by pathogen-recognition receptors, including nucleotide-binding leucin-rich repeats (NLRs) and receptor-like kinases (RLKs). We report a chromosome-level genome assembly of L. saligna (accession CGN05327), leading to the identification of two large paracentric inversions (>50 Mb) between L. saligna and L. sativa. Genome-wide searches delineated the major resistance clusters as regions enriched in NLRs and RLKs. Three of the enriched regions co-locate with previously identified NHR intervals. RNA-seq analysis of Bremia infected lettuce identified several differentially expressed RLKs in NHR regions. Three tandem wall-associated kinase-encoding genes (WAKs) in the NHR8 interval display particularly high expression changes at an early stage of infection. We propose RLKs as strong candidate(s) for determinants for the NHR phenotype of L. saligna.

genomics↗

bioRxiv2022

Structural and functional insights into the type III-E CRISPR-Cas immunity

The type III-E CRISPR-Cas system comprises a Cas effector (gRAMP), a TPR-CHAT and several ancillary proteins. However, both the structural features of gRAMP and the immunity mechanism remain unknown for this system. Here, we report a series of structures of gRAMP-crRNA, either its alone or in complex with target RNA or TPR-CHAT (called Craspase), and Craspase complexed with cognate (CTR) or non-cognate target RNA (NTR). Importantly, the 3 anti-tag region of NTR and CTR bind at two distinct channels in the Craspase, and CTR with a non-complementary 3 anti-tag induces a marked conformational change of the TPR-CHAT, which allosterically activates its protease activity to cleave an ancillary protein Csx30. This cleavage then triggers an abortive infection as the antiviral strategy of the type III-E system. Together, our study provides crucial insights into both the catalytic mechanism of the gRAMP and the immunity mechanism of the type III-E CRISPR-Cas system.

molecular biology↗

bioRxiv2022

An updated nomenclature for plant ribosomal protein genes

Ban et al. (2014) proposed a nomenclature for ribosomal proteins (r-proteins) that reflects the current understanding of ribosomal protein evolution. In the past few years, this nomenclature has been widely adopted among biomedical researchers and microbiologists. This homology-based r-protein nomenclature has not been as widely adopted among plant biologists, however, presumably because r-protein nomenclature is much more complicated in plants due to gene duplication. Here, we propose compatible upgrades to the homology-guided nomenclature proposed by Ban et al. (2014) so that this naming system can be adopted for widespread use in the plant biology community. We note that Lan et al. (2022) recently proposed updated nomenclature for plant cytosolic ribosomal proteins, focused on Arabidopsis and rice. The nomenclature outlined here is an extension of that proposed by Lan et al. (2022), expanding to include organellar ribosomes and additional species, with the intent that this nomenclature can serve as a template to guide future plant genome annotations. A more detailed comparison highlighting how this naming system builds on the Ban et al. (2014) and Lan et al. (2022) nomenclatures is offered below. At this time, we request community feedback on this proposed nomenclature so that the naming system ultimately chosen represents a broad consensus. Feedback can be communicated to the this working group at plantribosome@gmail.com before July 25th, 2022. Coauthors of this letter and anyone in the scientific community expressing significant interest will then discuss this feedback as a group, reach a consensus agreement, and communicate the updated nomenclature rules through a letter to the editor (expected to be published at The Plant Cell) and the databases at TAIR and MaizeGDB.

plant biology↗

bioRxiv2022

The genome of Gynandropsis gynandra provides insights into whole-genome duplications and the evolution of C4 photosynthesis in Cleomaceae

Gynandropsis gynandra (Cleomaceae) is a cosmopolitan leafy vegetable and medicinal plant, which has also been used as a model to study C4 photosynthesis due to its evolutionary proximity to Arabidopsis. Here, we present a high-quality genome sequence of G. gynandra, anchored onto 17 main super- scaffolds with a total length of 740 Mb, an N50 of 42 Mb and 30,933 well-supported gene models. The G. gynandra genome and previously released genomes of C3 relatives in the Cleomaceae and Brassicaceae make an excellent model for studying the role of genome evolution in the transition from C3 to C4 photosynthesis. We revealed that G. gynandra and its C3 relative Tarenaya hassleriana shared a whole-genome duplication event (Gg-), then an addition of a third genome (Th-, +1x) took place in T. hassleriana but not in G. gynandra. Analysis of syntenic copy number of C4 photosynthesis-related gene families indicates that G. gynandra generally retained more duplicated copies of these genes than C3 T. hassleriana, and also that the G. gynandra C4 genes might have been under positive selection pressure. Both whole-genome and single-gene duplication were found to contribute to the expansion of the aforementioned gene families in G. gynandra. Collectively, this study enhances our understanding of the impact of gene duplication and gene retention on the evolution of C4 photosynthesis in Cleomaceae.

plant biology↗

bioRxiv2022

Cable-free brain imaging with miniature wireless microscopes

The invention of the miniaturized microscope has enabled neuroscientists to investigate neural mechanisms in freely moving mice. A lot of efforts have been made to optimize performance of the miniaturized microscope. However, the tethered cables limit the ability of mini-microscope systems to record neural activity from multiple mice simultaneously. Here, we present a wireless mini-microscope (wScope) that enables both real-time remote control and data preview during animal behavior; this design also supports simultaneous recording from up to 8 mice. The wScope has a mass of 2.7 g and a maximum frame rate of 25 Hz at 750 m by 450 m field of view with 1.8 m resolution. We validated the wScopes in video-recording of the cerebral blood flow (CBF) and the activity of neurons in the primary visual cortex (V1) of different mice. The wScope provides a powerful tool for brain imaging of free moving animals, including large primates, in their much larger spaces and more naturalistic environments.

neuroscience↗

bioRxiv2022

A non-lemniscal thalamic interface connecting alerting sensory cues to internal states in mice

Alterations in internal states, such as elevated arousal level and increased anxiety or fear, triggered by alerting environmental cues are required for behavioral state transitions promoting survival. However, the specific brain region that plays an interfacing role between alerting stimuli and internal states remains to be identified. Here, we report that the medial sector of the auditory thalamus (ATm), which consists of a group of non-lemniscal thalamic nuclei, can fulfill this function. VGluT2-expressing ATm (ATmVGluT2+) neurons receive direct and strong inputs from both visual and auditory midbrain regions, and project to multiple downstream structures critically involved in brain state regulation. Their activity was correlated with, and indispensable for, both blue light- and sound-induced NREM sleep-to-Wake transition, and their arousing effects were mainly mediated by, but not limited to, the temporal association cortices. ATmVGluT2+ neuron activation in awake behaving mice induced pupil dilation and behavioral responses suggestive of anxiety. Blocking the neurotransmitter release of ATmVGluT2+ neurons receiving auditory inputs selectively abolished loud noise-triggered escape behavior but not locomotion. Thus, the ATm is an interface in mouse brain that can transform alerting environmental cues into internal arousal and emotional state alterations that promote survival.

neuroscience↗

bioRxiv2022

Regional and cell type-specific afferent and efferent projections of the mouse claustrum

The claustrum (CLA) is a conspicuous subcortical structure interconnected with cortical and subcortical regions. However, its regional anatomy and cell-type-specific connections in the mouse remain largely undetermined. Here, we accurately delineated the boundary of the mouse CLA and quantitatively investigated its inputs and outputs brain-wide using anterograde and retrograde viral tracing and fully reconstructed single claustral principal neurons. At a population level, the CLA reciprocally connects with all isocortical modules. It also receives inputs from at least 35 subcortical structures but sends projections back to only a few of them. We found that cell types projecting to the CLA are differentiated by cortical areas and layers. We classified single CLA principal neurons into at least 9 cell types that innervate the diverse sets of functionally linked cortical targets. Axons of interneurons within the CLA arborize along almost its entire anteroposterior extent. Together, this detailed wiring diagram of the cell-type-specific connections of the mouse CLA lays a foundation for studying its functions.

neuroscience↗

bioRxiv2022

Engineering SARS-CoV-2 cocktail antibodies into a bispecific format improves neutralizing potency and breadth

One major limitation of neutralizing antibody-based COVID-19 therapy is the requirement of costly cocktails to reduce antibody resistance. We engineered two bispecific antibodies (bsAbs) using distinct designs and compared them with parental antibodies and their cocktail. Single molecules of both bsAbs block the two epitopes targeted by parental antibodies on the receptor-binding domain (RBD). However, bsAb with the IgG-(scFv)2 design (14-H-06) but not the CrossMAb design (14-crs-06) increases antigen-binding and virus-neutralizing activities and spectrum against multiple SARS-CoV-2 variants including the Omicron, than the cocktail. X-ray crystallography and computational simulations reveal distinct neutralizing mechanisms for individual cocktail antibodies and suggest higher inter-spike crosslinking potentials by 14-H-06 than 14-crs-06. In mouse models of infections by SARS-CoV-2 and the Beta, Gamma, and Delta variants, 14-H-06 exhibits higher or equivalent therapeutic efficacy than the cocktail. Rationally engineered bsAbs represent a cost-effective alternative to antibody cocktails and a promising strategy to improve potency and breadth.

microbiology↗

bioRxiv2021

Homogeneity of antibody-drug conjugates critically impacts the therapeutic efficacy in brain tumors

Glioblastoma multiforme (GBM) is characterized by aggressive growth and the poorest prognosis of all brain tumor types. Most therapies rarely provide clinically meaningful improvements in outcomes of patients with GBM. Antibody-drug conjugates (ADCs) are emerging chemotherapeutics with stunning success in cancer management. Although promising, clinical studies of three ADCs for treating GBM, including Depatux-M, have been discontinued because of safety concerns and limited therapeutic benefits. Here, we report that ADC homogeneity is a critical parameter to maximize the therapeutic potential in GBM therapy. We demonstrate that homogeneous conjugates generated using our linker show enhanced drug delivery to intracranial brain tumors. Notably, compared to heterogeneous ADCs, including a Depatux-M analog, our ADCs provide greatly improved antitumor effects and survival benefits in orthotopic brain tumor models, including a patient-derived xenograft model of GBM. Our findings warrant the future development of homogeneous ADCs as promising molecular entities toward cures for intractable brain tumors.

bioengineering↗

bioRxiv2021

Active anaerobic methane oxidation and sulfur disproportionation in the deep terrestrial subsurface

Microbial life is widespread in the terrestrial subsurface and present down to several kilometers depth, but the energy sources that fuel metabolism in deep oligotrophic and anoxic environments remain unclear. In the deep crystalline bedrock of the Fennoscandian Shield at Olkiluoto, Finland, opposing gradients of abiotic methane and ancient seawater-derived sulfate create a terrestrial sulfate-methane transition zone (SMTZ). We used chemical and isotopic data coupled to genome-resolved metaproteogenomics to demonstrate active life and, for the first time, provide direct evidence of active anaerobic oxidation of methane (AOM) in a deep terrestrial bedrock. Proteins from Methanoperedens (formerly ANME-2d) are readily identifiable despite the low abundance ([≤]1%) of this genus and confirm the occurrence of AOM. This finding is supported by 13C-depleted dissolved inorganic carbon. Proteins from Desulfocapsaceae and Desulfurivibrionaceae, in addition to 34S-enriched sulfate, suggest that these organisms use inorganic sulfur compounds as both electron donor and acceptor. Zerovalent sulfur in the groundwater may derive from abiotic rock interactions, or from a non-obligate syntrophy with Methanoperedens, potentially linking methane and sulfur cycles in Olkiluoto groundwater. Finally, putative episymbionts from the candidate phyla radiation (CPR) and DPANN archaea represented a significant diversity in the groundwater (26/84 genomes) with roles in sulfur and carbon cycling. Our results highlight AOM and sulfur disproportionation as active metabolisms and show that methane and sulfur fuel microbial activity in the deep terrestrial subsurface. Significance StatementThe deep terrestrial subsurface remains an environment in which there is limited understanding of the extant microbial metabolisms, despite its reported large contribution to the overall biomass on Earth. It is much less well studied than deep marine sediments. We show that microorganisms in the subsurface are active, and that methane and sulfur provide fuel in the oligotrophic and anoxic subsurface. We also uncover taxonomically and metabolically diverse ultra-small organisms that interact with larger host cells through surface attachment (episymbiosis). Methane and sulfur are commonly reported in terrestrial crystalline bedrock environments worldwide and the latter cover a significant proportion of the Earths surface. Thus, methane- and sulfur-dependent microbial metabolisms have the potential to be widespread in the terrestrial deep biosphere.

microbiology↗

bioRxiv2021

Minimal-invasive enhancement of auditory perception by terahertz wave modulation

Hearing impairment is a common disease affecting a substantial proportion of the global population. Currently, the most effective clinical treatment for patients with sensorineural deafness is to implant an artificial electronic cochlea. However, the improvements to hearing perception are variable and limited among healthy subjects. Moreover, cochlear implants have disadvantages, such as crosstalk derived from the currents that spread into non-target tissue between the electrodes. Here, in this work, we describe terahertz wave modulation (THM), a new, minimally invasive technology that can enhance hearing perception in animals by reversible modulation of currents in cochlear hair cells. Using single-cell electrophysiology, guinea pig audiometry, and molecular dynamics simulations (MD), we show that THM can reversibly increase mechano-electrical transducer (MET) currents ([~]50% higher) and voltage-gated K+ currents in cochlear hair cells through collective resonance of -C=O groups. In addition, measurement of auditory brainstem response (ABR) in guinea pigs treated with THM indicated a [~]10 times increase in hearing sensitivity. This study thus reports a new method of highly spatially selective hearing enhancement without introducing any exogeneous gene, which has potential applications for treatment of hearing disorders as well as several other areas of neuroscience.

biophysics↗

bioRxiv2020

Antibody-drug conjugates with dual payloads for combating breast tumor heterogeneity and drug resistance

Breast tumors generally consist of a diverse population of cells with varying gene expression profiles. Breast tumor heterogeneity is a major factor contributing to drug resistance, recurrence, and metastasis after chemotherapy. Antibody-drug conjugates (ADCs) are emerging chemotherapeutic agents with striking clinical success, including T-DM1 for HER2-positive breast cancer. However, these ADCs often suffer from issues associated with intratumor heterogeneity. Here, we show that homogeneous ADCs containing two distinct payloads are a promising drug class for addressing this clinical challenge. Our conjugates show HER2-specific cell killing potency, desirable pharmacokinetic profiles, minimal immunogenicity, and marginal toxicity at therapeutic doses. Notably, a dual-drug ADC exerts greater treatment effect and survival benefit than does co-administration of two single-drug variants in a xenograft mouse model representing intratumor HER2 heterogeneity and elevated drug resistance. Our findings highlight the therapeutic potential of the dual-drug ADC format for treating refractory breast cancer and perhaps other cancers.

bioengineering↗

bioRxiv2020

ATP drives efficient terpene biosynthesis in marine thraustochytrids

Understanding carbon flux-controlling mechanisms in a tangled metabolic network is an essential question of cell metabolism. Secondary metabolism, such as terpene biosynthesis, has evolved with low carbon flux due to inherent pathway constraints. Thraustochytrids are a group of heterotrophic marine unicellular protists, and can accumulate terpenoids under the high salt condition in their natural environment. However, the mechanism behind the terpene accumulation is not well understood. Here we show that terpene biosynthesis in Thraustochytrium sp. ATCC 26185 is constrained by local thermodynamics in the mevalonate pathway. Thermodynamic analysis reveals the metabolite limitation in the nondecarboxylative Claisen condensation of acetyl-CoA to acetoacetyl-CoA step catalyzed by the acetyl-CoA acetyltransferase (ACAT). Through a sodium elicited mechanism, higher respiration leads to increased ATP investment into the mevalonate pathway, providing a strong thermodynamic driving force for enhanced terpene biosynthesis. The proteomic analysis further indicates that the increased ATP demands are fulfilled by shifting energy generation from carbohydrate to lipid metabolism. This study demonstrates a unique strategy in nature using ATP to drive a low-flux metabolic pathway, providing an alternative solution for efficient terpene metabolic engineering. IMPORTANCETerpenoids are a large class of lipid molecules with important biological functions, and diverse industrial and medicinal applications. Metabolic engineering for terpene production has been hindered by the low flux distribution to its biosynthesis pathway. In practice, a high substrate load is generally required to reach high product titers. Here we show that the mevalonate-derived terpene biosynthesis is constrained by local pathway thermodynamics, which can only be partially relieved by increasing substrate levels. Through comparative proteomic and biochemical analyses, we discovered a unique mechanism for high terpene accumulation in marine protists thraustochytrids. Through a sodium induced mechanism, thraustochytrids shift their energy metabolism from carbohydrate to lipid metabolism for enhanced ATP production, providing a strong thermodynamic driving force for efficient terpene biosynthesis. This study reveals an important mechanism in eukaryotes to overcome the thermodynamic constraint in low-flux pathways by increased ATP consumption. Engineering energy metabolism thus provides an important alternative to relieve flux constraints in low-flux and energy-consuming pathways.

systems biology↗

bioRxiv2020

Template-independent genome editing and repairing correct frameshift disease in vivo

Frameshift mutation caused by small insertions/deletions (indels) often generate truncated and non-functional proteins, which underlies 22% inherited Mendelian disorders in humans. However, there is no efficient in vivo gene therapy strategies available to date, especially in postmitotic systems. Here, we leveraged the non-homologous end joining (NHEJ) mediated non-random editing profiles to compensate the frameshift mutation in a USH1F mouse model - av3j. After treatment by the selected gRNA, about 50% editing products showed reading-frame restoration, and more than 70% targeted hair cells recovered mechanotransduction. In vivo treatment ameliorated the hearing and balance symptoms in homozygous mutant mice. Furthermore, a scale-up analysis of 114 gRNAs targeting 40 frameshift deafness mutations reveals that 65% loci have at least one gRNA with predicted therapeutic potential. Together, our study demonstrates that the NHEJ-mediated frame restoration is a simple and highly efficient therapeutic strategy for small-indel induced frameshift mutations.

neuroscience↗

bioRxiv2020

Piezo2 mediates ultrasonic hearing via cochlear outer hair cells in mice

Ultrasonic hearing is exploited for hunting and navigation as in echolocation by microbats and bottleneck dolphins, and for social communication like ultrasonic vocalization by mice and rats. However, the molecular and cellular basis for ultrasonic hearing is not known yet. Here we show that knockout of the mechanosensitive ion channel PIEZO2 in cochlea disrupts the ultrasonic hearing but not the low-frequency hearing in mice, as shown by audiometry and acoustically-associative freezing behavior. Deletion of Piezo2 in the outer hair cells specifically abolishes the associative learning of the mice upon hearing the ultrasonic frequency. Ex vivo cochlear Ca2+ imaging revealed that the ultrasonic transduction requires both PIEZO2 and the hair-cell mechanotransduction channel. Together, our study demonstrates that the outer hair cells are the effector cells with PIEZO2 as an essential molecule for ultrasonic hearing in mice. Significance StatementSome animals have evolved an incredible ability for vocalizing and hearing ultrasonic frequencies that is inaudible for humans (> 20 kHz). For many years, it has been considered that animals hear ultrasonic frequencies with their cochlear hair cells, using the identical set of mechanotransduction molecules in the hair bundles for hearing audible frequencies. Here, we show that the mice lacking the mechanosensitive ion channel PIEZO2 hardly hear ultrasonic frequencies, while can still be sensitive to audible frequencies. Thus, animals may use a partially different mechanism for sensing physiological ultrasound.

neuroscience↗

bioRxiv2020

Development of a simple in vitro assay to identify and evaluate nucleotide analogs against SARS-CoV-2 RNA-dependent RNA polymerase

Nucleotide analogs targeting viral RNA polymerase have been approved to be an effective strategy for antiviral treatment and are attracting antiviral drugs to combat the current SARS-CoV-2 pandemic. In this report, we develop a robust in vitro nonradioactive primer extension assay to evaluate the incorporation efficiency of nucleotide analog by SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) quantitively. Our results show that many nucleotide analogs can be incorporated into RNA by SARS-CoV-2 RdRp, and that the incorporation of some of them leads to chain termination. The discrimination values of nucleotide analog over those of natural nucleotide were measured to evaluate the incorporation efficiency of nucleotide analog by RdRp. We found that the incorporation efficiency of Remdesivir-TP is higher than ATP, and we did not observe chain termination or delayed chain termination caused by single Remdesivir-TP incorporation, while multiple incorporations of Remdesivir-TP caused chain termination in our assay condition. The incorporation efficiency of Ribavirin-TP and Favipiravir-TP is very low either as ATP or GTP analogs, which suggested that mutagenesis may not be the mechanism of action of those two drugs against SARS-CoV-2. Incorporation of Sofosbuvir-TP is also very low suggesting that sofosbuvir may not be very effective in treating SARS-CoV-2 infection. As a comparison, 2-C-Methyl-GTP can be incorporated into RNA efficiently, and the derivative of 2-C-Methyl-GTP may have therapeutic application in treating SARS-CoV-2 infection. This report provides a simple screening method that should be useful in evaluating nucleotide-based drugs targeting SARS-CoV-2 RdRp, and for studying the mechanism of action of selected nucleotide analog.

biochemistry↗