NRDE2 negatively regulates exosome functions by inhibiting MTR4 recruitment and exosome interaction.

The exosome functions in the degradation of diverse RNA species, yet how it is negatively regulated remains largely unknown. Here, we show that NRDE2 forms a 1:1 complex with MTR4, a nuclear exosome cofactor critical for exosome recruitment, via a conserved MTR4-interacting domain (MID). Unexpectedly, NRDE2 mainly localizes in nuclear speckles, where it inhibits MTR4 recruitment and RNA degradation, and thereby ensures efficient mRNA nuclear export. Structural and biochemical data revealed that NRDE2 interacts with MTR4's key residues, locks MTR4 in a closed conformation, and inhibits MTR4 interaction with the exosome as well as proteins important for MTR4 recruitment, such as the cap-binding complex (CBC) and ZFC3H1. Functionally, MID deletion results in the loss of self-renewal of mouse embryonic stem cells. Together, our data pinpoint NRDE2 as a nuclear exosome negative regulator that ensures mRNA stability and nuclear export.

PM2.5 induce neurotoxicity via iron overload and redox imbalance mediated-ferroptosis in HT22 cells.

PM2.5 is an important risk factor for the development and progression of cognitive impairment-related diseases. Ferroptosis, a new form of cell death driven by iron overload and lipid peroxidation, is proposed to have significant implications. To verify the possible role of ferroptosis in PM2.5-induced neurotoxicity, we investigated the cytotoxicity, intracellular iron content, iron metabolism-related genes, oxidative stress indices and indicators involving in Nrf2 and ferroptosis signaling pathways. Neurotoxicity biomarkers as well as the ferroptotic cell morphological changes were determined by Western Blot and TEM analysis. Our results revealed that PM2.5 induced cytotoxicity, lipid peroxidation, as indicated by MDA content, and neurotoxicity via Aß deposition in a dose-related manner. Decreased cell viability and excessive iron accumulation in HT-22 cells can be partially blocked by ferroptosis inhibitors. Interestingly, GPX activity, Nrf2, and its regulated ferroptotic-related proteins (i.e. GPX4 and HO-1) were significantly up-regulated by PM2.5. Moreover, gene expression of DMT1, TfR1, IRP2 and FPN1 involved in iron homeostasis and NCOA4-dependent ferritinophagy were activated after PM2.5 exposure. The results demonstrated that PM2.5 triggered ferritinophagy-dependent ferroptotic cell death due to iron overload and redox imbalance. Activation of Nrf2 signaling pathways may confer a protective mechanism for PM2.5-induced oxidative stress and ferroptosis.

ALYREF links 3'-end processing to nuclear export of non-polyadenylated mRNAs.

The RNA-binding protein ALYREF plays key roles in nuclear export and also 3'-end processing of polyadenylated mRNAs, but whether such regulation also extends to non-polyadenylated RNAs is unknown. Replication-dependent (RD)-histone mRNAs are not polyadenylated, but instead end in a stem-loop (SL) structure. Here, we demonstrate that ALYREF prevalently binds a region next to the SL on RD-histone mRNAs. SL-binding protein (SLBP) directly interacts with ALYREF and promotes its recruitment. ALYREF promotes histone pre-mRNA 3'-end processing by facilitating U7-snRNP recruitment through physical interaction with the U7-snRNP-specific component Lsm11. Furthermore, ALYREF, together with other components of the TREX complex, enhances histone mRNA export. Moreover, we show that 3'-end processing promotes ALYREF recruitment and histone mRNA export. Together, our results point to an important role of ALYREF in coordinating 3'-end processing and nuclear export of non-polyadenylated mRNAs.

Validating HONO as an Intermediate Tracer of the External Cycling of Reactive Nitrogen in the Background Atmosphere.

In the urban atmosphere, nitrogen oxide (NOx═NO + NO2)-related reactions dominate the formation of nitrous acid (HONO). Here, we validated an external cycling route of HONO and NOx, i.e., formation of HONO resulting from precursors other than NOx, in the background atmosphere. A chemical budget closure experiment of HONO and NOx was conducted at a background site on the Tibetan Plateau and provided direct evidence of the external cycling. An external daytime HONO source of 100 pptv h-1 was determined. Both soil emissions and photolysis of nitrate on ambient surfaces constituted likely candidate mechanisms characterizing this external source. The external source dominated the chemical production of NOx with HONO as an intermediate tracer. The OH production was doubled as a result of the external cycling. A high HONO/NOx ratio (0.31 ± 0.06) during the daytime was deduced as a sufficient condition for the external cycling. Literature review suggested the prevalence of high HONO/NOx ratios in various background environments, e.g., polar regions, pristine mountains, and forests. Our analysis validates the prevalence of external cycling in general background atmosphere and highlights the promotional role of external cycling regarding the atmospheric oxidative capacity.

ZFC3H1 prevents RNA trafficking into nuclear speckles through condensation.

Controlling proper RNA pool for nuclear export is important for accurate gene expression. ZFC3H1 is a key controller that not only facilitates nuclear exosomal degradation, but also retains its bound polyadenylated RNAs in the nucleus upon exosome inactivation. However, how ZFC3H1 retains RNAs and how its roles in RNA retention and degradation are related remain largely unclear. Here, we found that upon degradation inhibition, ZFC3H1 forms nuclear condensates to prevent RNA trafficking to nuclear speckles (NSs) where many RNAs gain export competence. Systematic mapping of ZFC3H1 revealed that it utilizes distinct domains for condensation and RNA degradation. Interestingly, ZFC3H1 condensation activity is required for preventing RNA trafficking to NSs, but not for RNA degradation. Considering that no apparent ZFC3H1 condensates are formed in normal cells, our study suggests that nuclear RNA degradation and retention are two independent mechanisms with different preference for controlling proper export RNA pool-degradation is preferred in normal cells, and condensation retention is activated upon degradation inhibition.

Additive-Controlled Divergent Synthesis of Indole and 4H-Benzo[d][1,3]oxazine Derivatives: Palladium-Catalyzed Carbonylative Cyclization of 2-Alkynylanilines and Benzyl Chlorides.

A palladium-catalyzed divergent carbonylative synthesis of indoles and 4H-benzo[d][1,3]oxazines from 2-alkynylanilines and benzyl chlorides with benzene-1,3,5-triyl triformate (TFBen) as the CO source has been developed. The reaction using AlCl3 as the additive produced various indoles in high yields, while a series of 4H-benzo[d][1,3]oxazines was achieved in moderate yields with AcOH as the additive.

A U2-snRNP-independent role of SF3b in promoting mRNA export.

To ensure efficient and accurate gene expression, pre-mRNA processing and mRNA export need to be balanced. However, how this balance is ensured remains largely unclear. Here, we found that SF3b, a component of U2 snRNP that participates in splicing and 3' processing of pre-mRNAs, interacts with the key mRNA export adaptor THO in vivo and in vitro. Depletion of SF3b reduces THO binding with the mRNA and causes nuclear mRNA retention. Consistently, introducing SF3b binding sites into the mRNA enhances THO recruitment and nuclear export in a dose-dependent manner. These data demonstrate a role of SF3b in promoting mRNA export. In support of this role, SF3b binds with mature mRNAs in the cells. Intriguingly, disruption of U2 snRNP by using a U2 antisense morpholino oligonucleotide does not inhibit, but promotes, the role of SF3b in mRNA export as a result of enhanced SF3b-THO interaction and THO recruitment to the mRNA. Together, our study uncovers a U2-snRNP-independent role of SF3b in mRNA export and suggests that SF3b contributes to balancing pre-mRNA processing and mRNA export.

Palladium-catalyzed carbonylative synthesis of aryl esters from p-benzoquinones and aryl triflates.

A palladium-catalyzed dicarbonylation of p-benzoquinones with aryl triflates has been developed. Using Cr(CO)6 as the CO source, the reaction proceeds smoothly and efficiently to give a series of aryl esters in moderate to good yields (up to 90%).

Silver nanoparticles: Correlating particle size and ionic Ag release with cytotoxicity, genotoxicity, and inflammatory responses in human cell lines.

The widespread use of silver nanoparticles (AgNPs), their many sources for human exposure, and the ability of AgNPs to enter organisms and induce general toxicological responses have raised concerns regarding their public health and environmental safety. To elucidate the differential toxic effects of polyvinylpyrrolidone-capped AgNPs with different primary particle sizes (i.e. 5, 50, and 75 nm), we performed a battery of cytotoxicity and genotoxicity assays and examined the inflammatory responses in two human cell lines (i.e. HepG2 and A549). Concentration-dependent decreases in cell proliferation and mitochondrial membrane potential and increases in cytokine (i.e. interleukin-6 and interleukin-8) excretion indicated disruption of mitochondrial function and inflammation as the main mediating factors of AgNPs-induced cytotoxicity. An incremental increase in genotoxicity with decreasing AgNPs diameter was noted in HepG2 cells, which was associated with S and G2/M accumulation and transcriptional activation of the GADD45α promoter as reflected by luciferase activity. Dose-related genetic damage, as indicated by Olive tail moment and micronucleus formation, was also observed in A549 cells, but these effects as well as the AgNPs-induced cytotoxicity were more associated with ionic Ag release from nanoparticles (NPs). In summary, the present study addressed different toxicity mechanisms of AgNPs, depending on the cell model, toxicological endpoint, particle size, and degree of Ag+ release from NPs. The results suggest that the GADD45α promoter-driven luciferase reporter cell system provided a rapid screening tool for the identification of genotoxic properties of NPs across a range of different sizes and concentrations.

Chelating Group Enabled Palladium-Catalyzed Regiodivergent Carbonylative Synthesis of 2,3-Dihydroquinolin-4(1H)-ones.

A new procedure on palladium-catalyzed carbonylative cyclization of N-(2-pyridyl)sulfonyl (N-SO2 Py)-2-iodoanilines with terminal alkenes has been developed for the rapid construction of dihydroquinolin-4(1H)-one scaffolds. Enabled by the chelating group and using benzene-1,3,5-triyl triformate (TFBen) as the CO source, both aromatic and aliphatic alkenes were smoothly transformed into the corresponding 2,3-dihydroquinolin-4(1H)-ones in good yields with excellent regioselectivities. Notably, the reaction of aromatic alkenes produces 2-aryl-2,3-dihydroquinolin-4(1H)-ones, while 3-alkyl-2,3-dihydroquinolin-4(1H)-ones were obtained when aliphatic alkenes were used. This protocol has been applied in the synthesis of antitumor agent A as well.

A Protocol for the Synthesis of CF2H-Containing Pyrazolo[1,5- c]quinazolines from 3-Ylideneoxindoles and in Situ Generated CF2HCHN2.

Herein is disclosed a selective and facile approach for the construction of CF2H-containing pyrazolo[1,5- c]quinazolines from easily accessible 3-ylideneoxindoles and in situ generated CF2HCHN2. The reaction involving a [3 + 2] cycloaddition/1,3-H shift/rearrangement/dehydrogenation cascade proceeded smoothly at room temperature in the absence of catalyst and additive. Moreover, this metal-free process along with mild conditions is desirable and valuable for the pharmaceutical industry. Importantly, this reaction features a broad substrate scope, good functional group tolerance, and gram-scale synthesis.

Sparse Method for Direction of Arrival Estimation Using Denoised Fourth-Order Cumulants Vector.

Fourth-order cumulants (FOCs) vector-based direction of arrival (DOA) estimation methods of non-Gaussian sources may suffer from poor performance for limited snapshots or difficulty in setting parameters. In this paper, a novel FOCs vector-based sparse DOA estimation method is proposed. Firstly, by utilizing the concept of a fourth-order difference co-array (FODCA), an advanced FOCs vector denoising or dimension reduction procedure is presented for arbitrary array geometries. Then, a novel single measurement vector (SMV) model is established by the denoised FOCs vector, and efficiently solved by an off-grid sparse Bayesian inference (OGSBI) method. The estimation errors of FOCs are integrated in the SMV model, and are approximately estimated in a simple way. A necessary condition regarding the number of identifiable sources of our method is presented that, in order to uniquely identify all sources, the number of sources K must fulfill K ≤ ( M 4 - 2 M 3 + 7 M 2 - 6 M ) / 8 . The proposed method suits any geometry, does not need prior knowledge of the number of sources, is insensitive to associated parameters, and has maximum identifiability O ( M 4 ) , where M is the number of sensors in the array. Numerical simulations illustrate the superior performance of the proposed method.

Diastereoselective [3 + 2] cycloaddition of 3-ylideneoxindoles with in situ generated CF2HCHN2: syntheses of CF2H-containing spirooxindoles.

An efficient [3 + 2] cycloaddition of 3-ylideneoxindoles with in situ generated CF2HCHN2 for the syntheses of spirooxindoles has been developed. This methodology gives access to a range of relatively complex spirooxindoles featuring a CF2H group and three contiguous stereogenic centers in up to 84% yield and 99 : 1 trans/cis.

Development of HSPA1A promoter-driven luciferase reporter gene assays in human cells for assessing the oxidative damage induced by silver nanoparticles.

The exponential increase in the total number of engineered nanoparticles in consumer products requires novel tools for rapid and cost-effective toxicology screening. In order to assess the oxidative damage induced by nanoparticles, toxicity test systems based on a human HSPA1A promoter-driven luciferase reporter in HepG2, LO2, A549, and HBE cells were established. After treated with heat shock and a group of silver nanoparticles (AgNPs) with different primary particle sizes, the cell viability, oxidative damage, and luciferase activity were determined. The time-dependent Ag(+) ions release from AgNPs in cell medium was also evaluated. Our results showed that heat shock produced a strong time-dependent induction of relative luciferase activity in the four luciferase reporter cells. Surprisingly, at 4h of recovery, the relative luciferase activity was >98× the control level in HepG2-luciferase cells. Exposure to different sizes of AgNPs resulted in activation of the HSPA1A promoter in a dose-dependent manner, even at low cytotoxic or non-cytotoxic doses. The smaller (5nm) AgNPs were more potent in luciferase induction than the larger (50 and 75nm) AgNPs. These results were generally in accordance with the oxidative damage indicated by malondialdehyde concentration, reactive oxygen species induction and glutathione depletion, and Ag(+) ions release in cell medium. Compared with the other three luciferase reporter cells, the luciferase signal in HepG2-luciferase cells is obviously more sensitive and stable. We conclude that the luciferase reporter cells, especially the HepG2-luciferase cells, could provide a valuable tool for rapid screening of the oxidative damage induced by AgNPs.

Oxidative stress and mitochondrial injury-mediated cytotoxicity induced by silver nanoparticles in human A549 and HepG2 cells.

OBJECTIVES: Considering the increasing applications of silver nanoparticles (AgNPs) in food- and cosmetic-related products worldwide, the aim of this study was to investigate the potential adverse health effects induced by AgNPs exposure in terms of cytotoxicity, oxidative stress, and mitochondrial injury in human A549 and HepG2 cells. METHODS: After a 48 h AgNPs treatment, the cell viability was measured by MTT assay. Oxidative damage was determined by assays of malondialdehyde (MDA), 8-epi-PGF2α and 8-hydroxy-2'-deoxyguanosine (8-oxo-dG). The protein expression of HSPA1A and HO-1 was analyzed by western blot analysis. Mitochondrial membrane potential (MMP) was detected by using JC-1 as fluorescent probes. The uptake and intracellular localization of AgNPs was measured by transmission electron microscopy (TEM), and cellular AgNPs was determined by inductively coupled plasma mass spectrometry (ICP-MS). RESULTS: A dose-dependent decrease in cell viability after AgNPs treatment was observed, which was associated correspondingly with oxidative damage as indicated by increases in MDA amount, 8-epi-PGF2α and 8-oxo-dG levels, HSPA1A and HO-1 expression, as well as mitochondrial injury as indicated by decreased MMP. The cellular uptake of AgNPs measured by ICP-MS analysis was correlated correspondingly with the oxidative damage and mitochondrial injury. CONCLUSIONS: The dose-dependent cytotoxicity induced by AgNPs may result from an interaction of oxidative stress, DNA damage and mitochondrial injury in A549 and HepG2 cells. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1691-1699, 2016.

The development of GADD45α luciferase reporter assays in human cells for assessing the genotoxicity of environmental pollutants.

OBJECTIVES: In order to assess the potential carcinogenic and genotoxic responses induced by environmental pollutants, genotoxicity test systems based on a GADD45α promoter-driven luciferase reporter in human A549 and HepG2 cells were established. MATERIALS AND METHODS: Four different types of environmental toxicants including DNA alkylating agents, precarcinogenic agents, DNA cross-linking agents and non-carcinogenic agents, and three environmental samples collected from a coke oven plant were used to evaluate the test systems. After treated with the tested agents and environmental samples for 12 h, the cell viabilities and luciferase activities of the luciferase reporter cells were determined, respectively. RESULTS: Methyl methanesulfonate, benzo[a]pyrene, formaldehyde and the extractable organic matter (EOM) from coke oven emissions in ambient air generally produced significant induction of relative luciferase activity in a similar dose-dependent manner in A549- and HepG2-luciferase cells. No significant increases in relative luciferase activity were observed in pyrene-treated A549- or HepG2-luciferase cells. Significant increase in relative luciferase activity was already evident after 2.5 µM benzo[a]pyrene, 5 µM formaldehyde, 0.006 µg/L bottom-EOM, 0.10 µg/L side-EOM or 0.06 µg/L top-EOM, where no cytotoxic damage was observed. Compared with the A549-luciferase cells, the tested pollutants produced higher induction of relative luciferase activity in HepG2-luciferase cells. DISCUSSION AND CONCLUSION: Therefore, the new genotoxicity test systems can detect different types of genotoxic agents and low concentrations of environmental samples. The luciferase reporter cells, especially the HepG2-luciferase cells, could provide a valuable tool for rapid screening of the genotoxic damage of environmental pollutants and their complex mixtures.

Optimizing a twin-chamber system for direct ozone production rate measurement.

High Ozone Production Rate (OPR) leads to O3 pollution episodes and adverse human health outcomes. OPR observation (Obs-OPR) and OPR modelling (Mod-OPR) have been obtained from observed and modelled peroxy radicals and nitrogen oxides. However, discrepancies between them remind of an imperfect understanding of O3 photochemistry. Direct measurement of OPR (Mea-OPR) by a twin-chamber system emerges. Herein, we optimized Mea-OPR design, i.e., minimizing the chamber surface area to volume ratio (S/V) to 9.8 m-1 from 18 m-1 and the dark uptake coefficient of O3 to 9.9 × 10-9 from 7.1 × 10-8 in the literature. In addition, control experiments further revealed and quantified a photo-enhanced O3 uptake, and therefore recommended an essential correction of Mea-OPR. We finally characterized a measurement uncertainty of ±38% and a detection limit of 3.2 ppbv h-1 (3SD), which suggested that Mea-OPR would be sensitive enough to measure OPR in urban or suburban environments. Further application of this system in urban Beijing during the Beijing 2022 Olympic Winter Games recorded a noontime OPR of 7.3 (±3.3, 1SD) ppbv h-1. These observational results added up to our confidence in future field application of Mea-OPR, to facilitate pollution control policy evaluation and to shed light on O3 photochemistry puzzle.

Interfacial and Defective Construction from Diverse CuxSy Quantum Dots toward Broadband Carbon-Based Microwave Absorber.

In this study, highly monodisperse copper sulfide (CuxSy) quantum dots (QDs) have been successfully obtained using a ligand-chemistry strategy, and then a variety of S-deficient CuxSy/nitrogen-doped carbon (NC) heterointerfaces are constructed by compositional fine-tuning (Cu9S5 → Cu1.96S → Cu). First-principles calculations show that the S-deficient domains of CuxSy QDs and N-doped domains of carbon synergistically enhance the electron transfer from CuxSy to NC. In addition, the finite element simulations demonstrate that the diverse CuxSy QDs exhibit their intrinsic size and dielectric confinement effects to precisely manipulate the electric field distortion and improve the relaxation polarization. Consequently, CuxSy@NC achieves excellent impedance matching and a strong loss mode dominated by dielectric polarization. Among them, CuxSy@NC-650 has a maximum effective absorption bandwidth of 7.7 GHz at 2.5 mm, while CuxSy@NC-700 features a minimum reflection loss of -66.7 dB at 13.7 GHz, respectively. Furthermore, the simulations of radar cross-sections have confirmed that the CuxSy@NC series is promising in the field of radar stealth.

Silver nanoparticles induce iron accumulation-associated cognitive impairment via modulating neuronal ferroptosis.

Silver nanoparticles (AgNPs) are widely used in daily life and medical fields owing to their unique physicochemical properties. Daily exposure to AgNPs has become a great concern regarding their potential toxicity to human beings, especially to the central nervous system. Ferroptosis, a newly recognized programmed cell death, was recently reported to be associated with the neurodegenerative process. However, whether and how ferroptosis contributes to AgNPs-induced neurotoxicity remain unclear. In this study, we investigated the role of ferroptosis in neurotoxic effects induced by AgNPs using in vitro and in vivo models. Our results showed that AgNPs induced a notable dose-dependent cytotoxic effect on HT-22 cells and cognitive impairment in mice as indicated by a decline in learning and memory and brain tissue injuries. These findings were accompanied by iron overload caused by the disruption of the iron transport system and activation of NCOA4-mediated autophagic degradation of ferritin. The excessive free iron subsequently induced GSH depletion, loss of GPX and SOD activities, differential expression of Nrf2 signaling pathway elements, down-regulation of GPX4 protein and production of lipid peroxides, initiating ferroptosis cascades. The mitigating effects of ferrostatin-1 and deferoxamine on iron overload, redox imbalance, neuronal cell death, impairment of mice learning and memory, Aß deposition and synaptic plasticity reduction suggested ferroptosis as a potential molecular mechanism in AgNPs-induced neurotoxicity. Taken together, these results demonstrated that AgNPs induced neuronal cell death and cognitive impairment with Aß deposition and reduction of synaptic plasticity, which were mediated by ferroptosis caused by iron-mediated lipid peroxidation. Our study provides new insights into the underlying mechanisms of AgNPs-induced neurotoxicity and predicts potential preventive strategies.

Metabolic labeling based methylome profiling enables functional dissection of histidine methylation in C3H1 zinc fingers.

Protein methylation is a functionally important post-translational modification that occurs on diverse amino acid residues. The current proteomics approaches are inefficient to discover the methylation on residues other than Arg and Lys, which hinders the deep understanding of the functional role of rare protein methylation. Herein, we present a methyl-specific metabolic labeling approach for global methylome mapping, which enable the acquisition of methylome dataset covering diverse methylation types. Interestingly, of the identified methylation events, His methylation is found to be preferably occurred in C3H1 zinc fingers (ZFs). These His methylation events are determined to be Nπ specific and catalyzed by CARNMT1. The His methylation is found to stabilize the structure of ZFs. U2AF1 is used as a proof-of-concept to highlight the functional importance of His methylation in ZFs in RNA binding and RNA metabolism. The results of this study enable novel understanding of how protein methylation regulates cellular processes.