Entry Channel Research Articles

Structure of Gcn1 bound to stalled and colliding 80S ribosomes

The Gcn pathway is conserved in all eukaryotes, including mammals such as humans, where it is a crucial part of the integrated stress response (ISR). Gcn1 serves as an essential effector protein for the kinase Gcn2, which in turn is activated by stalled ribosomes, leading to phosphorylation of eIF2 and a subsequent global repression of translation. The fine-tuning of this adaptive response is performed by the Rbg2/Gir2 complex, a negative regulator of Gcn2. Despite the wealth of available biochemical data, information on structures of Gcn proteins on the ribosome has remained elusive. Here we present a cryo-electron microscopy structure of the yeast Gcn1 protein in complex with stalled and colliding 80S ribosomes. Gcn1 interacts with both 80S ribosomes within the disome, such that the Gcn1 HEAT repeats span from the P-stalk region on the colliding ribosome to the P-stalk and the A-site region of the lead ribosome. The lead ribosome is stalled in a nonrotated state with peptidyl-tRNA in the A-site, uncharged tRNA in the P-site, eIF5A in the E-site, and Rbg2/Gir2 in the A-site factor binding region. By contrast, the colliding ribosome adopts a rotated state with peptidyl-tRNA in a hybrid A/P-site, uncharged-tRNA in the P/E-site, and Mbf1 bound adjacent to the mRNA entry channel on the 40S subunit. Collectively, our findings reveal the interaction mode of the Gcn2-activating protein Gcn1 with colliding ribosomes and provide insight into the regulation of Gcn2 activation. The binding of Gcn1 to a disome has important implications not only for the Gcn2-activated ISR, but also for the general ribosome-associated quality control pathways.

Difference in demographics and motivation to study medicine with respect to medical students’ channel of admission: A national study

Introduction Medical schools employ various tools to select suitable medical students (MS). This study investigated whether MS who were admitted through multiple mini-interviews (MMI) and MS who were admitted through Taiwan’s Joint College Entrance Written Test (JCEWT) differed in their characteristics. Methods and subjects First-year MS from seven medical schools completed a semi-structured questionnaire that inquired into their channel of admission (MMI or JCEWT), gender, location (metropolitan or rural), high school type (public or private), parents’ socioeconomic status (SES), and motivations to study medicine. Results In total, 513 MS participated, 493 (96%) returned valid questionnaires, and 397 were enrolled in the study, (MMI group: 205 MS; JCEWT group: 192 MS). Irrespective of channel of admission, most MS came from metropolitan areas (80%–86%), belonged to high-SES families (73%–76%), and had mixed motivations (51%–96%). Female applicants, private school leavers, and those who were less motivated by the physician’s SES were more likely to be selected through the MMI channel than the JCEWT channel. Conclusion Irrespective of the channels of entry, MS had similar demographics and motivations for studying medicine. MS selected through MMI had different characteristics than those selected through a JCEWT.

V for versatility: TRPV4 Ca2+ entry channel plays multiple roles in invadosome regulation

Several Ca2+-permeable cation channels attract attention for their mechanotransducer function to evoke Ca2+ signals in cell invasion. Vellino et al., have clarified the versatility of the osmo-sensing TRPV4 channel in regulating invadosome functions: TRPV4 detects and integrates multiple cellular and environmental cues, triggering Ca2+ signals and molecular interactions that modulate coupling between acto-adhesion and extracellular matrix degradation.

Activation of TRPV4 channels leads to a consistent tocolytic effect on human myometrial tissues.

Human myometrium is a therapeutic target for labor induction and preterm labor. This study aimed to assess the physiological role of alternative calcium conductance on contractions triggered by uterotonic drugs in human myometrium. Membrane conductances, supported by TRPV channels, may provide alternative pathways to control either free intracellular and/or submembrane Ca2+-concentration, which in turn will modulate membrane polarization and contractile responses. Uterine biopsies were obtained from consenting women undergoing elective caesarean delivery at term without labor (N = 22). Isometric tension measurements were performed on uterine smooth muscle strips (n = 132). Amplitude, frequency, and area under the curve (AUC) of phasic contractions, as well as resting tone, were measured under various experimental conditions. Immuno histo- and cyto-chemistry, as well as Western blot analyses, have been performed with specific antibodies against TRPV1, TRPV3, and TRPV4 proteins. TRPV4 agonists; GSK1016790A, 4αPDD, and 5,6-EET were used to assess the role of TRPV4 channels on rhythmic activity triggered by 30-300 nM oxytocin. 5 μM of ruthenium red was used as an efficient blocker of ionic current through TRPV4 channels. Nanomolar concentrations of iberiotoxin (IbTX) were also used to confirm the downstream involvement of BKCa channels in controlling uterine reactivity and contractility. The expression of TRPV3 and TRPV4 isoforms has now been demonstrated in human myometrial tissue and cell culture. Nanomolar concentrations of the TRPV4 agonists, (either GSK1016790A or 4αPDD) abolished the rhythmic contractions, resulting in a rapid and consistent tocolytic effect. While 5 μM of ruthenium reversed this tocolytic effect. The addition of IbTX (a BKCa channel blocker) reversed the effects of GSK1016790A. Carvacrol, a TRPV3 agonist, had similar tocolytic effects on rhythmic contractions albeit at higher concentrations. This inhibitory effect was also reversed by ruthenium red. Collectively, these data suggest that activation of TRPV4 leads to a Ca2+ entry and subsequent BKCa channel activation (increase in open state probability), which in turn hyperpolarizes the myometrial cell membrane, inactivating L-type Ca2+ channels and efficiently abrogates contractile activity. Consequently, alternative Ca2+ conductance supported by TRPV4 plays a physiological role in the modulation of myometrial reactivity.

Mechanism of the Activation of Ribosome Rescue Factor ArfB

Messenger RNAs (mRNAs) which lack a stop codon result in ribosomes stalled at the 3’ end of the mRNA. Alternative ribosome-rescue factor B (ArfB) rescues stalled ribosomes by tRNA-peptide hydrolysis and thus releasing the peptide. ArfB consists of an N-terminal domain with the GGQ motif required for the hydrolysis, a C-terminal domain which acts as a sensor for the empty mRNA entry channel, and a linker connecting the domains. ArfB binds to the ribosomal A site regardless of the length of the truncated mRNA.

Dynamic competition between SARS-CoV-2 NSP1 and mRNA on the human ribosome inhibits translation initiation

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a beta-CoV that recently emerged as a human pathogen and is the causative agent of the COVID-19 pandemic. A molecular framework of how the virus manipulates host cellular machinery to facilitate infection remains unclear. Here, we focus on SARS-CoV-2 NSP1, which is proposed to be a virulence factor that inhibits protein synthesis by directly binding the human ribosome. We demonstrate biochemically that NSP1 inhibits translation of model human and SARS-CoV-2 messenger RNAs (mRNAs). NSP1 specifically binds to the small (40S) ribosomal subunit, which is required for translation inhibition. Using single-molecule fluorescence assays to monitor NSP1-40S subunit binding in real time, we determine that eukaryotic translation initiation factors (eIFs) allosterically modulate the interaction of NSP1 with ribosomal preinitiation complexes in the absence of mRNA. We further elucidate that NSP1 competes with RNA segments downstream of the start codon to bind the 40S subunit and that the protein is unable to associate rapidly with 80S ribosomes assembled on an mRNA. Collectively, our findings support a model where NSP1 proteins from viruses in at least two subgenera of beta-CoVs associate with the open head conformation of the 40S subunit to inhibit an early step of translation, by preventing accommodation of mRNA within the entry channel.

Lithium Reduces Migration and Collagen Synthesis Activity in Human Cardiac Fibroblasts by Inhibiting Store-Operated Ca2+ Entry.

Cardiac fibrosis plays a vital role in the pathogenesis of heart failure. Fibroblast activity is enhanced by increases in store-operated Ca2+ entry (SOCE) and calcium release-activated calcium channel protein 1 (Orai1) levels. Lithium regulates SOCE; however, whether therapeutic concentrations of lithium can be used to inhibit cardiac fibrogenesis is unknown. Migration and proliferation assays, Western blotting, real-time reverse-transcription polymerase chain reaction analysis, and calcium fluorescence imaging were performed in human cardiac fibroblasts treated with or without LiCl at 1.0 mM (i.e., therapeutic peak level) or 0.1 mM (i.e., therapeutic trough level) for 24 h. Results showed that LiCl (0.1 mM, but not 1.0 mM) inhibited the migration and collagen synthesis ability of cardiac fibroblasts. Additionally, thapsigargin-induced SOCE was reduced in fibroblasts treated with LiCl (0.1 mM). The expression level of Orai1 was lower in LiCl (0.1 mM)-treated fibroblasts relative to the fibroblasts without LiCl treatment. Fibroblasts treated with a combination of LiCl (0.1 mM) and 2-APB (10 μM, an Orai1 inhibitor) demonstrated similar migration and collagen synthesis abilities as those in LiCl (0.1 mM)-treated fibroblasts. Altogether, lithium at therapeutic trough levels reduced the migration and collagen synthesis abilities of human cardiac fibroblasts by inhibiting SOCE and Orai1 expression.

Calcium Sensors STIM1 and STIM2 Regulate Different Calcium Functions in Cultured Hippocampal Neurons.

There are growing indications for the involvement of calcium stores in the plastic properties of neurons and particularly in dendritic spines of central neurons. The store-operated calcium entry (SOCE) channels are assumed to be activated by the calcium sensor stromal interaction molecule (STIM)which leads to activation of its associated Orai channel. There are two STIM species, and the differential role of the two in SOCE is not entirely clear. In the present study, we were able to distinguish between transfected STIM1, which is more mobile primarily in young neurons, and STIM2 which is less mobile and more prominent in older neurons in culture. STIM1 mobility is associated with spontaneous calcium sparks, local transient rise in cytosolic [Ca2+]i, and in the formation and elongation of dendritic filopodia/spines. In contrast, STIM2 is associated with older neurons, where it is mobile and moves into dendritic spines primarily when cytosolic [Ca2+]i levels are reduced, apparently to activate resident Orai channels. These results highlight a role for STIM1 in the regulation of [Ca2+]i fluctuations associated with the formation of dendritic spines or filopodia in the developing neuron, whereas STIM2 is associated with the maintenance of calcium entry into stores in the adult neuron.

FRET Sensors Reveal the Retinal Entry Pathway in the G Protein-Coupled Receptor Rhodopsin

The visual photoreceptor rhodopsin (Rho) represents a curious case among G protein-coupled receptors (GPCRs) because its primary ligand 11-cis-retinal (11CR) is an inverse agonist, which partitions into the bilayer and enters through an intermembranous pathway. Light activates Rho by converting 11CR to all-trans-retinal (ATR), which serves as an agonist ligand. We used genetic code expansion and bioorthogonal labeling to engineer Rho mutants that serve as FRET sensors for measuring 11CR binding kinetics and energetics. We found mutations that alter a channel between transmembrane helices 5 and 6 (TM5/6) dramatically affect 11CR binding kinetics, but not ATR release kinetics. Our data provide direct experimental evidence for 11CR entry between TM5/6 in Rho that involves dynamic allosteric control of the ligand entry channel. Our findings can be extended to other visual pigments and a wide range of GPCRs with hydrophobic ligands that are hypothesized to enter their binding pockets through transmembrane pores.

The End of Human Rights Dynamism? Judgments of the ECtHR on ‘Hot Returns’ and Humanitarian Visas as a Focal Point of Contemporary European Asylum Law and Policy

Abstract Two controversial rulings of the Grand Chamber of the European Court of Human Rights (ECtHR) deserve global attention, since they declined to scrutinize on human rights grounds the prevalent move towards enhanced border controls and externalization practices that define European asylum law and policy at this juncture. In ND and NT, judges deemed the Spanish policy of ‘hot returns’, without access to basic procedural guarantees, of those climbing border fences to be compatible with human rights. A few weeks later, the Grand Chamber thwarted enduring hopes for judicial innovation in MN when it reasserted a ‘primarily territorial’ understanding of State jurisdiction and declared inadmissible the claim of a Syrian family from the war-torn town of Aleppo to a humanitarian visa. While the decision on humanitarian visas means that ‘non-arrival’ policies cannot usually be challenged, critical inspection of the ND and NT judgment displays a confounding combination of restrictive arguments and dynamic elements beneath the surface of a seemingly clear-cut outcome. This lack of judicial precision, which was bound to cause heated debate about the practical implications of the judgment, reflects the basic tension between the prohibition of refoulement and the absence of a right to asylum in classic accounts of international refugee law. It will be argued that the judicial vindication of the Spanish ‘hot returns’ policy does not call into question non-refoulement obligations; it aims at identifying graded procedural standards for different categories of refugees and migrants. By contrast, the novel insistence on the abstract availability of legal channels of entry presents itself as a humanitarian fig leaf for the acceptance of strict control practices. At an intermediate level of abstraction, the two rulings mark a watershed moment, indicating the provisional endpoint of an impressive period of interpretative dynamism on the part of the ECtHR, which has played a critical role in the progressive evolution of international refugee and human rights law over the past three decades. Experts in asylum law who have become accustomed to supranational courts advancing the position of individuals will benefit from the insights of constitutional theory and the social sciences to rationalize why the former vigour has given way to a period of hesitation and potential standstill, at least in Europe. This analysis employs the perspective of strategic litigation to discuss contextual factors hindering the continued dynamism of human rights jurisprudence in Europe at this juncture.

A structural inventory of native ribosomal ABCE1‐43S pre‐initiation complexes

In eukaryotic translation, termination and ribosome recycling phases are linked to subsequent initiation of a new round of translation by persistence of several factors at ribosomal sub‐complexes. These comprise/include the large eIF3 complex, eIF3j (Hcr1 in yeast) and the ATP‐binding cassette protein ABCE1 (Rli1 in yeast). The ATPase is mainly active as a recycling factor, but it can remain bound to the dissociated 40S subunit until formation of the next 43S pre‐initiation complexes. However, its functional role and native architectural context remains largely enigmatic. Here, we present an architectural inventory of native yeast and human ABCE1‐containing pre‐initiation complexes by cryo‐EM. We found that ABCE1 was mostly associated with early 43S, but also with later 48S phases of initiation. It adopted a novel hybrid conformation of its nucleotide‐binding domains, while interacting with the N‐terminus of eIF3j. Further, eIF3j occupied the mRNA entry channel via its ultimate C‐terminus providing a structural explanation for its antagonistic role with respect to mRNA binding. Overall, the native human samples provide a near‐complete molecular picture of the architecture and sophisticated interaction network of the 43S‐bound eIF3 complex and the eIF2 ternary complex containing the initiator tRNA.

The viral protein NSP1 acts as a ribosome gatekeeper for shutting down host translation and fostering SARS-CoV-2 translation.

SARS-CoV-2 coronavirus is responsible for the Covid-19 pandemic. In the early phase of infection, the single-strand positive RNA genome is translated into nonstructural proteins (NSP). One of the first proteins produced during viral infection, NSP1, binds to the host ribosome and blocks the mRNA entry channel. This triggers translation inhibition of cellular translation. Despite the presence of NSP1 on the ribosome, viral translation proceeds, however. The molecular mechanism of the so-called viral evasion to NSP1 inhibition remains elusive. Here, we confirm that viral translation is maintained in the presence of NSP1 and we show that the evasion to NSP1-inhibition is mediated by the cis-acting RNA hairpin SL1 in the 5′UTR of SARS-CoV-2. Only the apical part of SL1 is required for viral translation. We further show that NSP1 remains bound on the ribosome during viral translation. We suggest that the interaction between NSP1 and SL1 frees the mRNA accommodation channel while maintaining NSP1 bound to the ribosome. Thus, NSP1 acts as a ribosome gatekeeper, shutting down host translation and fostering SARS-CoV-2 translation in the presence of the SL1 5′UTR hairpin. SL1 is also present and necessary for translation of subgenomic RNAs in the late phase of the infectious program. Consequently, therapeutic strategies targeting SL1 should affect viral translation at early and late stages of infection. Therefore, SL1 might be seen as a genuine “Achilles heel” of the virus.

Informal recruitment channels, family background and university enrolments in Italy

This paper analyses the impact of informal recruitment channels on university enrolment decisions. A widespread diffusion of personal connections as an entry channel to the labour market may signal that social ties to well-off people are necessary to get a good job, thereby convincing students from poorly connected families that getting a tertiary education degree does not enhance their future socio-economic opportunities. By applying estimation techniques with instrumental variables to Italian microdata, I found that upper-secondary students coming from lower social classes are less likely to participate in tertiary education when they live in provinces where the percentage of newly tertiary graduates who found a job through informal channels is higher. My results are consistent with the hypothesis that the wide diffusion of ‘favouritism’ in local labour markets engenders a sense of ‘economic despair’ among poorly connected students, thereby worsening inequality of access to education and local socio-economic development.literature and the hypothesis

Quantification of soya-based feed ingredient entry from ASFV-positive countries to the United States by ocean freight shipping and associated seaports.

African swine fever virus (ASFV) can survive in soya‐based products for 30 days with T ½ ranging from 9.6 to 12.9 days in soya bean meals and soya oil cake. As the United States imports soya‐based products from several ASFV‐positive countries, knowledge of the type and quantity of these specific imports, and their ports of entry (POE), is necessary information to manage risk. Using the data from the International Trade Commission Harmonized Tariff Schedule website in conjunction with pivot tables, we analysed imports across air, land and sea POE of soya‐based products from 43 ASFV‐positive countries to the United States during 2018 and 2019. In 2018, 104,366 metric tons (MT) of soya‐based products, specifically conventional and organic soya bean meal, soya beans, soya oil cake and soya oil were imported from these countries into the United States via seaports only. The two largest suppliers were China (52.7%, 55,034 MT) and the Ukraine (42.9%, 44,775 MT). In 2019, 73,331 MT entered the United States and 54.7% (40,143 MT) came from the Ukraine and 8.4% (6,182 MT) from China. Regarding POE, 80.9%–83.2% of soya‐based imports from China entered the United States at the seaports of San Francisco, CA, and Seattle, WA, while 89.4%–100% entered from the Ukraine via the seaports of New Orleans, LA, and Charlotte, NC. Analysis of five‐year trends (2015–2019) of the volume of soya imports from China indicated reduction over time (with a noticeably sharp decrease between 2018 and 2019), and seaport utilization was consistent. In contrast, volume remained high for Ukrainian soya imports, and seaport utilization was inconsistent. Overall, this exercise introduced a new approach to collect objective data on an important risk factor, providing researchers, government officials and industry stakeholders a means to objectively identify and quantify potential channels of foreign animal disease entry into the United States.

Molecular docking studies of 1, 3, 4 oxadiazoles Derivatives as anti-convulsive agents

Molecular docking is a computational technique that places a small molecule (ligand) in the binding site of its macromolecular target (receptor) and estimates its binding affinity. The present study attempted the high throughput in-silico screening of 65 compounds docked with the GABAA receptor (PDB ID: 4COF) using Molegro virtual docker (6.0). Out of these 65 compounds, 17 compounds showed very good mol dock score in ranging between -66.344 & -102.653. Ethosuximide and Carbamazepine drugs was used as a standard drug which showed mol dock score -50.6357 & -58.5047 respectively. Most of test compounds demonstrated excellent number of hydrogen bond interactions viz compounds 33, 38, 39, 45, 47, 53, 54, 59, 61, 62, 63, 64 & 65 which showed 7 to 11 number of hydrogen bond interactions as compared to standard drug interactions values 6 & 5 respectively and also showed the interaction with same amino acids Glu52, Ser51and Val53 and some other amino acids Asn54, Thr58 and Thr133 also showed very acceptable bond length less than 3.91Å. The obtained results indicated that all studied ligands have similar position and orientation inside the putative binding site of GABAA receptor (PDB ID: 4COF) which reveals a large space bounded by a membrane-binding domain which serves as an entry channel for substrate to the active site. In addition, the affinity of any small molecule can be considered as a unique tool in the field of drug design and offer prospective in future research to develop a potent anticonvulsant agent.

Nonstructural Protein 1 of SARS-CoV-2 Is a Potent Pathogenicity Factor Redirecting Host Protein Synthesis Machinery toward Viral RNA

The causative virus of the COVID-19 pandemic, SARS-CoV-2, uses its nonstructural protein 1 (Nsp1) to suppress cellular, but not viral, protein synthesis through yet unknown mechanisms. We show here that among all viral proteins, Nsp1 has the largest impact on host viability in the cells of human lung origin. Differential expression analysis of mRNA-seq data revealed that Nsp1 broadly alters the cellular transcriptome. Our cryo-EM structure of the Nsp1-40S ribosome complex shows that Nsp1 inhibits translation by plugging the mRNA entry channel of the 40S. We also determined the structure of the 48S preinitiation complex formed by Nsp1, 40S, and the cricket paralysis virus internal ribosome entry site (IRES) RNA, which shows that it is nonfunctional because of the incorrect position of the mRNA 3′ region. Our results elucidate the mechanism of host translation inhibition by SARS-CoV-2 and advance understanding of the impacts from a major pathogenicity factor of SARS-CoV-2.

The Bank Entry Channel of Monetary Policy Transmission

We provide causal evidence of the deposits channel of monetary policy transmission in a new setting, but show that bank entry can reduce or even reverse the relationship between deposit market structure and monetary policy pass-through. We build a simple model of monetary policy transmission when deposit market structure is endogenous. In our model, expansionary monetary policy decreases bank funding costs and stimulates bank entry, which in turn stimulates aggregate credit provision. Using novel shocks to bank entry barriers, we confirm the model’s main predictions: the deposits channel exists, but local establishment and employment growth increase more in response to expansionary monetary policy when bank entry barriers are lower. Our results suggest that the deposits channel and the effects of expansionary monetary policy are tamed when bank entry costs are high, as is currently the case.

An attempt to chemically state the cross-talk between monomers of COX homodimers by double/hybrid inhibitors mofezolac-spacer-mofezolac and mofezolac-spacer-arachidonic acid.

Cardiovascular diseases (CVDs) account for over 17 million death globally each year, including arterial thrombosis. Platelets are key components in the pathogenesis of this disease and modulating their activity is an effective strategy to treat such thrombotic events. Cyclooxygenase-1 (COX-1) isoenzyme is involved in platelet activation and is the main target of non-steroidal anti-inflammatory drugs (NSAIDs) and new selective inhibitor research. Inhibitors of general formula mofezolac-spacer-mofezolac (mof-spacer-mof) and mofezolac-spacer-arachidonic acid (mof-spacer-AA) were projected to investigate the possible cross-talk between the two monomers (Eallo and Ecat) forming the COX-1 homodimer. Mofezolac was chosen as either one or two moieties of these molecules being the known most potent and selective COX-1 inhibitor and administrated to humans as Disopain™, then arachidonic acid (AA) was used to develop molecules bearing, in the same compound, in addition to the inhibitor moiety (mofezolac) also the natural COX substrate. Depending on the nature of the spacer, COX-1 and COX-2 activity was differently inhibited by mof-spacer-mof set with a preferential COX-1 inhibition. The highest COX-1 selectivity was exhibited by the compound in which the spacer was the benzidine [N,N'-(biphenyl-4,4'-di-yl)bis (2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamide) (15): COX-1 IC50=0.08μM, COX-2 IC50>50μM, Selectivity Index (SI)>625]. In the case of mof-spacer-AA set, the COX inhibitory potency and also the isoform preference changed. (5Z, 8Z, 11Z, 14Z)-N-(4-{2-[3,4-Bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}butyl)icosa-5,8,11,14-tetraenamide (19) and (5Z, 8Z, 11Z, 14Z)-N-(4'-{2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}-[1,1'-biphenyl]-4-yl)icosa-5,8,11,14-tetraenamide (21), in which the spacer is the 1,2-diaminobutane or benzidine, respectively, selectively inhibited the COX-2, whereas when the spacer is the 1,4-phenylendiamine [(5Z, 8Z, 11Z, 14Z)-N-(4-{2-[3,4-bis(4-methoxyphenyl)isoxazol-5-yl]acetamido}phenyl)icosa-5,8,11,14-tetraenamide) (20) the COX preference is COX-1 (COX-1 IC50=0.05μM, COX-2 IC50>50μM, with a COX-1 selectivity>1000). Molecular modelling by using FLAP algorithm shows fundamental interactions of the novel compounds at the entry channel of COX and inside its catalytic cavity. The effect of these mof-spacer-mof and mof-spacer-AA in inhibiting invitro free arachidonic acid-induced platelet aggregation was also determined. A positive profile of hemocompatibility in relation to their influence on the blood coagulation cascade and erythrocyte toxicity was observed. Cytotoxicity and genotoxicity safety were also found for these two novel sets of compounds.

SARS-CoV-2 Disrupts Splicing, Translation, and Protein Trafficking to Suppress Host Defenses

SummarySevere acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a recently identified coronavirus that causes the respiratory disease known as coronavirus disease 2019 (COVID-19). Despite the urgent need, we still do not fully understand the molecular basis of SARS-CoV-2 pathogenesis. Here, we comprehensively define the interactions between SARS-CoV-2 proteins and human RNAs. NSP16 binds to the mRNA recognition domains of the U1 and U2 splicing RNAs and acts to suppress global mRNA splicing upon SARS-CoV-2 infection. NSP1 binds to 18S ribosomal RNA in the mRNA entry channel of the ribosome and leads to global inhibition of mRNA translation upon infection. Finally, NSP8 and NSP9 bind to the 7SL RNA in the signal recognition particle and interfere with protein trafficking to the cell membrane upon infection. Disruption of each of these essential cellular functions acts to suppress the interferon response to viral infection. Our results uncover a multipronged strategy utilized by SARS-CoV-2 to antagonize essential cellular processes to suppress host defenses.

Cyclical Fluctuations, Financial Shocks, and the Entry of Fast-Growing Entrepreneurial Startups

Abstract We analyze a multiyear, multicountry entrepreneurship survey with more than one million observations to identify startups with low and high growth potential. We confirm the validity of these ex ante measures with ex post firm-level information on employment growth. We find that negative aggregate financial shocks reduce all startup types, but their effect is significantly stronger for startups with high growth potential, especially when GDP growth is low. Our results uncover a new composition of entry channel that significantly reduces employment growth and is potentially important for explaining slow recoveries after financial crises.