Structure and dynamics of SARS-CoV-2 proofreading exoribonuclease ExoN.

High-fidelity replication of the large RNA genome of coronaviruses (CoVs) is mediated by a 3'-to-5' exoribonuclease (ExoN) in nonstructural protein 14 (nsp14), which excises nucleotides including antiviral drugs misincorporated by the low-fidelity viral RNA-dependent RNA polymerase (RdRp) and has also been implicated in viral RNA recombination and resistance to innate immunity. Here, we determined a 1.6-Å resolution crystal structure of severe acute respiratory syndrome CoV 2 (SARS-CoV-2) ExoN in complex with its essential cofactor, nsp10. The structure shows a highly basic and concave surface flanking the active site, comprising several Lys residues of nsp14 and the N-terminal amino group of nsp10. Modeling suggests that this basic patch binds to the template strand of double-stranded RNA substrates to position the 3' end of the nascent strand in the ExoN active site, which is corroborated by mutational and computational analyses. We also show that the ExoN activity can rescue a stalled RNA primer poisoned with sofosbuvir and allow RdRp to continue its extension in the presence of the chain-terminating drug, biochemically recapitulating proofreading in SARS-CoV-2 replication. Molecular dynamics simulations further show remarkable flexibility of multidomain nsp14 and suggest that nsp10 stabilizes ExoN for substrate RNA binding to support its exonuclease activity. Our high-resolution structure of the SARS-CoV-2 ExoN-nsp10 complex serves as a platform for future development of anticoronaviral drugs or strategies to attenuate the viral virulence.

Structural basis for recognition of distinct deaminated DNA lesions by endonuclease Q.

Spontaneous deamination of DNA cytosine and adenine into uracil and hypoxanthine, respectively, causes C to T and A to G transition mutations if left unrepaired. Endonuclease Q (EndoQ) initiates the repair of these premutagenic DNA lesions in prokaryotes by cleaving the phosphodiester backbone 5' of either uracil or hypoxanthine bases or an apurinic/apyrimidinic (AP) lesion generated by the excision of these damaged bases. To understand how EndoQ achieves selectivity toward these structurally diverse substrates without cleaving undamaged DNA, we determined the crystal structures of Pyrococcus furiosus EndoQ bound to DNA substrates containing uracil, hypoxanthine, or an AP lesion. The structures show that substrate engagement by EndoQ depends both on a highly distorted conformation of the DNA backbone, in which the target nucleotide is extruded out of the helix, and direct hydrogen bonds with the deaminated bases. A concerted swing motion of the zinc-binding and C-terminal helical domains of EndoQ toward its catalytic domain allows the enzyme to clamp down on a sharply bent DNA substrate, shaping a deep active-site pocket that accommodates the extruded deaminated base. Within this pocket, uracil and hypoxanthine bases interact with distinct sets of amino acid residues, with positioning mediated by an essential magnesium ion. The EndoQ-DNA complex structures reveal a unique mode of damaged DNA recognition and provide mechanistic insights into the initial step of DNA damage repair by the alternative excision repair pathway. Furthermore, we demonstrate that the unique activity of EndoQ is useful for studying DNA deamination and repair in mammalian systems.

Molecular Dynamics Simulation and Kinetic Study of Fluoride Binding to V21C/V66C Myoglobin with a Cytoglobin-like Disulfide Bond.

Protein design is able to create artificial proteins with advanced functions, and computer simulation plays a key role in guiding the rational design. In the absence of structural evidence for cytoglobin (Cgb) with an intramolecular disulfide bond, we recently designed a de novo disulfide bond in myoglobin (Mb) based on structural alignment (i.e., V21C/V66C Mb double mutant). To provide deep insight into the regulation role of the Cys21-Cys66 disulfide bond, we herein perform molecular dynamics (MD) simulation of the fluoride-protein complex by using a fluoride ion as a probe, which reveals detailed interactions of the fluoride ion in the heme distal pocket, involving both the distal His64 and water molecules. Moreover, we determined the kinetic parameters of fluoride binding to the double mutant. The results agree with the MD simulation and show that the formation of the Cys21-Cys66 disulfide bond facilitates both fluoride binding to and dissociating from the heme iron. Therefore, the combination of theoretical and experimental studies provides valuable information for understanding the structure and function of heme proteins, as regulated by a disulfide bond. This study is thus able to guide the rational design of artificial proteins with tunable functions in the future.

A radiomics nomogram based on multiparametric MRI might stratify glioblastoma patients according to survival.

OBJECTIVES: To construct a radiomics nomogram for the individualized estimation of the survival stratification in glioblastoma (GBM) patients using the multiregional information extracted from multiparametric MRI, which could facilitate the clinical decision-making for GBM patients. MATERIALS AND METHODS: A total of 105 eligible GBM patients (57 in the long-term and 48 in the short-term survival groups, separated by an overall survival of 12 months) were selected from the Cancer Genome Atlas. These patients were divided into a training set (n = 70) and a validation set (n = 35). Radiomics features (n = 4000) were extracted from multiple regions of the GBM using multiparametric MRI. Then, a radiomics signature was constructed using least absolute shrinkage and selection operator regression for each patient in the training set. Combined with clinical risk factors, a radiomics nomogram was constructed based on a multivariate logistic regression model. The performance of this radiomics nomogram was assessed by calibration, discrimination, and clinical usefulness. RESULTS: The radiomics signature consisted of 25 selected features and performed better than clinical risk factors (i.e., age, Karnofsky performance status, and treatment strategy) in survival stratification. When the radiomics signature and clinical risk factors were combined, the radiomics nomogram exhibited promising discrimination in the training (C-index, 0.971) and validation (C-index, 0.974) sets. The favorable calibration and decision curve analysis indicated the clinical usefulness of the radiomics nomogram. CONCLUSIONS: The presented radiomics nomogram, as a non-invasive prediction tool, could exhibit a favorable predictive accuracy and provide individualized probabilities of survival stratification for GBM patients. KEY POINTS: • Non-invasive survival stratification of GBM patients can be obtained with a radiomics nomogram. • The proposed nomogram constructed by radiomics signature selected from 4000 radiomics features, combined with independent clinical risk factors such as age, Karnofsky performance status, and treatment strategy. • The proposed radiomics nomogram exhibited good calibration and discrimination for survival stratification of GBM patients in both training (C-index, 0.971) and validation (C-index, 0.974) sets.

Structure and function of an ancestral-type ß-decarboxylating dehydrogenase from Thermococcus kodakarensis.

ß-Decarboxylating dehydrogenases, which are involved in central metabolism, are considered to have diverged from a common ancestor with broad substrate specificity. In a molecular phylogenetic analysis of 183 ß-decarboxylating dehydrogenase homologs from 84 species, TK0280 from Thermococcus kodakarensis was selected as a candidate for an ancestral-type ß-decarboxylating dehydrogenase. The biochemical characterization of recombinant TK0280 revealed that the enzyme exhibited dehydrogenase activities toward homoisocitrate, isocitrate, and 3-isopropylmalate, which correspond to key reactions involved in the lysine biosynthetic pathway, tricarboxylic acid cycle, and leucine biosynthetic pathway, respectively. In T. kodakarensis, the growth characteristics of the KUW1 host strain and a TK0280 deletion strain suggested that TK0280 is involved in lysine biosynthesis in this archaeon. On the other hand, gene complementation analyses using Thermus thermophilus as a host revealed that TK0280 functions as both an isocitrate dehydrogenase and homoisocitrate dehydrogenase in this organism, but not as a 3-isopropylmalate dehydrogenase, most probably reflecting its low catalytic efficiency toward 3-isopropylmalate. A crystallographic study on TK0280 binding each substrate indicated that Thr71 and Ser80 played important roles in the recognition of homoisocitrate and isocitrate while the hydrophobic region consisting of Ile82 and Leu83 was responsible for the recognition of 3-isopropylmalate. These analyses also suggested the importance of a water-mediated hydrogen bond network for the stabilization of the ß3-α4 loop, including the Thr71 residue, with respect to the promiscuity of the substrate specificity of TK0280.

The effect of glioblastoma heterogeneity on survival stratification: a multimodal MR imaging texture analysis.

Background Quantitative evaluation of the effect of glioblastoma (GBM) heterogeneity on survival stratification would be critical for the diagnosis, treatment decision, and follow-up management. Purpose To evaluate the effect of GBM heterogeneity on survival stratification, using texture analysis on multimodal magnetic resonance (MR) imaging. Material and Methods A total of 119 GBM patients (65 in long-term and 54 in short-term survival group, separated by overall survival of 12 months) were selected from the Cancer Genome Atlas, who underwent the T1-weighted (T1W) contrast-enhanced (CE), T1W, T2-weighted (T2W), and FLAIR sequences. For each sequence, the co-occurrence matrix, run-length matrix, and histogram features were extracted to reflect GBM heterogeneity on different scale. The recursive feature elimination based support vector machine was adopted to find an optimal subset. Then the stratification performance of four MR sequences was evaluated, both alone and in combination. Results When each sequence used alone, the T1W-CE sequence performed best, with an area under the receiver operating characteristic curve, accuracy, sensitivity, and specificity of 0.7915, 80.67%, 78.45%, and 83.33%, respectively. When the four sequences combined, the stratification performance was basically equal to that of T1W-CE sequence. In the optimal subset of features extracted from multimodality, those from the T2W sequence weighted the most. Conclusion All the four sequences could reflect heterogeneous distribution of GBM and thereby affect the survival stratification, especially T1W-CE and T2W sequences. However, the stratification performance using only the T1W-CE sequence can be preserved with omission of other three sequences, when investigating the effect of GBM heterogeneity on survival stratification.

Effect of extracorporeal shock wave combined with Kinesio taping on upper limb function during individuals with biceps brachii tendinopathy：protocol for a double-blind, randomised controlled trial.

INTRODUCTION: Long head of biceps brachii tendinopathy (LHBT) is characterised by persistent pain and disability of shoulder joint, impairing patients' quality of life. Extracorporeal shock wave therapy (ESWT) is a non-invasive treatment, which promotes tissue regeneration and repair. However, ESWT has a side effect that often causes short-term pain and swelling in the treatment area. It is known that the effects of Kinesio taping (KT) on relieving swelling and pain. Due to insufficient clinical evidence from current limited studies, this randomised controlled study aims to explore the effects of ESWT combined with KT on upper limb function during individuals with LHBT. METHODS AND ANALYSIS: A 2×2 factorial design, double-blind, randomised controlled trial will be conducted. A total of 144 participants will be randomly allocated into one of four groups (KT+ESWT, KT+sham ESWT, sham KT+ESWT or sham KT+sham ESWT) to participate in a 4-week treatment programme. Measurements will be taken at pretreatment (baseline), immediately after treatment and 6 weeks after treatment. The primary endpoint will be the Constant-Murley score (CMS), the secondary endpoints will include the pain Numerical Rating Scale, range of motion, pressure pain threshold and soft tissue hardness of biceps, speed test and global rating of change. Repeated measures analysis of variance will be used to compare differences among the effects of different interventions. ETHICS AND DISSEMINATION: Ethics approval was obtained from the Ethics Committee of the Shanghai Sixth People's Hospital Affiliated to Shanghai Jiao Tong University School of Medicine. In addition to international conference reports, findings will be disseminated through international publications in peer-reviewed journals. TRIAL REGISTRATION NUMBER: ChiCTR2100051324.

Structural basis of sequence-specific cytosine deamination by double-stranded DNA deaminase toxin DddA.

The interbacterial deaminase toxin DddA catalyzes cytosine-to-uracil conversion in double-stranded (ds) DNA and enables CRISPR-free mitochondrial base editing, but the molecular mechanisms underlying its unique substrate selectivity have remained elusive. Here, we report crystal structures of DddA bound to a dsDNA substrate containing the 5'-TC target motif. These structures show that DddA binds to the minor groove of a sharply bent dsDNA and engages the target cytosine extruded from the double helix. DddA Phe1375 intercalates in dsDNA and displaces the 5' (-1) thymine, which in turn replaces the target (0) cytosine and forms a noncanonical T-G base pair with the juxtaposed guanine. This tandem displacement mechanism allows DddA to locate a target cytosine without flipping it into the active site. Biochemical experiments demonstrate that DNA base mismatches enhance the DddA deaminase activity and relax its sequence selectivity. On the basis of the structural information, we further identified DddA mutants that exhibit attenuated activity or altered substrate preference. Our studies may help design new tools useful in genome editing or other applications.

Osteogenic and anti-inflammatory effect of the multifunctional bionic hydrogel scaffold loaded with aspirin and nano-hydroxyapatite.

Although tissue engineering offered new approaches to repair bone defects, it remains a great challenge to create a bone-friendly microenvironment and rebuild bone tissue rapidly by a scaffold with a bionic structure. In this study, a multifunctional structurally optimized hydrogel scaffold was designed by integrating polyvinyl alcohol (PVA), gelatin (Gel), and sodium alginate (SA) with aspirin (ASA) and nano-hydroxyapatite (nHAP). The fabrication procedure is through a dual-crosslinking process. The chemical constitution, crystal structure, microstructure, porosity, mechanical strength, swelling and degradation property, and drug-release behavior of the hydrogel scaffold were analyzed. Multi-hydrogen bonds, electrostatic interactions, and strong "egg-shell" structure contributed to the multi-network microstructure, bone tissue-matched properties, and desirable drug-release function of the hydrogel scaffold. The excellent performance in improving cell viability, promoting cell osteogenic differentiation, and regulating the inflammatory microenvironment of the prepared hydrogel scaffold was verified using mouse pre-osteoblasts (MC3T3-E1) cells. And the synergistic osteogenic and anti-inflammatory functions of aspirin and nano-hydroxyapatite were also verified. This study provided valuable insights into the design, fabrication, and biological potential of multifunctional bone tissue engineering materials with the premise of constructing a bone-friendly microenvironment.

Corrigendum: Osteogenic and anti-inflammatory effect of the multifunctional bionic hydrogel scaffold loaded with aspirin and nano-hydroxyapatite.

[This corrects the article DOI: 10.3389/fbioe.2023.1105248.].

ELABELA protects against diabetic kidney disease by activating high glucose-inhibited renal tubular autophagy.

ELABELA (ELA), an endogenous ligand of the apelin receptor (also known as apelin peptide jejunum [APJ]), has been shown to decrease in the plasma of patients with diabetic kidney disease (DKD). In the current study, we explored the potential function as well as the underlying mechanisms of ELA in DKD. We first found that the ELA levels were decreased in the kidneys of DKD mice. Then, we found that ELA administration mitigated renal damage and downregulated the expression of fibronectin, collagen Ⅳ, and transforming growth factor-ß1 in the db/db mice and the high glucose cultured HK-2 cells. Furthermore, the autophagy markers, Beclin-1 and LC3-Ⅱ/LC3-Ⅰ ratio, were significantly impaired in DKD, but the ELA treatment reversed these alterations. Mechanistically, the inhibitory effects of ELA on the secretion of fibrosis-associated proteins in high glucose conditions were blocked by pretreatment with 3-methyladenine (an autophagy inhibitor). In summary, these in vivo and in vitro results demonstrate that ELA effectively protects against DKD by activating high glucose-inhibited renal tubular autophagy, potentially serving as a novel therapeutic candidate for DKD.

Kaempferol attenuates doxorubicin-induced renal tubular injury by inhibiting ROS/ASK1-mediated activation of the MAPK signaling pathway.

BACKGROUND AND OBJECTIVE: Doxorubicin (DOX) is one of the most commonly used antineoplastic agents; however, its considerable nephrotoxicity restricts its clinical use. Kaempferol (KPF), a naturally-occurring flavonoid, possesses various biological benefits, including anti-tumor activity that has garnered increasing attention. This study aimed to evaluate the possible reno-protective role of KPF in DOX nephrotoxicity. METHODS: Male BALB/c mice were injected with DOX via the tail vein to imitate renal damage. Their body and kidney were weighed after 2 weeks of KPF therapy, and urine, serum, and tissue samples were obtained to establish proteinuria, serum creatinine, and pathological alterations. The variations in SOD, GSH, CTA, MDA, and SOD2 expression in renal tissues were measured, and p-ASK1, p-p38, and P-JNK were evaluated by western blot. Cell viability was detected using MTT tests. Apoptosis was assessed by TUNEL, Hoechst 33342, PI staining, and western blot. Fluorescent ROS probes were used to assess oxidative cell damage. RESULTS: KPF ameliorated DOX-induced renal injury, improved proteinuria and renal function, restored GSH content, SOD activity and CTA activity in kidneys, inhibited the overproduction of MDA, and suppressed DOX-induced activation of the MAPK signaling pathway. In NRK-52E cells, KPF significantly inhibited DOX-induced ROS overproduction, restrained the activation of MAPK signaling pathway, and alleviated DOX-induced cell morphological damage and loss of cell viability, While it did not affect the toxicity of DOX to 4T1 cells. CONCLUSION: KPF provides a protective effect against DOX-induced nephrotoxicity while maintaining the cytotoxicity of DOX in breast cancer cells, thereby it may provide a viable solution to lessen renal toxicity in cancer patients receiving DOX.

Surface effects on kinematics, kinetics and stiffness of habitual rearfoot strikers during running.

The surface effects on running biomechanics have been greatly investigated. However, the effects on rearfoot strike runners remain unknown. The purpose of this study was to investigate the effects of surfaces on the running kinematics, kinetics, and lower-limb stiffness of habitual rearfoot strikers. Thirty healthy male runners were recruited to run at 3.3 ± 0.2 m/s on a customized runway covered with three different surfaces (artificial grass, synthetic rubber, or concrete), and their running kinematics, kinetics, and lower-limb stiffness were compared. Differences among the three surfaces were examined using statistical parametric mapping and one-way repeated-measure analysis of variance. There were no statistical differences in the lower-limb joint motion, vertical ground reaction force (GRF), loading rates, and lower-limb stiffness when running on the three surfaces. The braking force (17%-36% of the stance phase) and mediolateral GRF were decreased when running on concrete surface compared with running on the other two surfaces. The moments of ankle joint in all three plane movement and frontal plane hip and knee joints were increased when running on concrete surface. Therefore, habitual rearfoot strikers may expose to a higher risk of running-related overuse injuries when running on a harder surface.

Antagonism among DUX family members evolved from an ancestral toxic single homeodomain protein.

Double homeobox (DUX) genes are unique to eutherian mammals and normally expressed transiently during zygotic genome activation. The canonical member, DUX4, is involved in facioscapulohumeral muscular dystrophy (FSHD) and cancer, when misexpressed in other contexts. We evaluate the 3 human DUX genes and the ancestral single homeobox gene sDUX from the non-eutherian mammal, platypus, and find that DUX4 activities are not shared with DUXA or DUXB, which lack transcriptional activation potential, but surprisingly are shared with platypus sDUX. In human myoblasts, platypus sDUX drives cytotoxicity, inhibits myogenesis, and induces DUX4 target genes, particularly those associated with zygotic genome activation (ZGA), by binding DNA as a homodimer in a way that overlaps the DUX4 homeodomain crystal structure. DUXA lacks transcriptional activity but has DNA-binding and chromatin accessibility overlap with DUX4 and sDUX, including on ZGA genes and LTR elements, and can actually be converted into a DUX4-like cytotoxic factor by fusion to a synthetic transactivation domain. DUXA competition antagonizes the activity of DUX4 on its target genes, including in FSHD patient cells. Since DUXA is an early DUX4 target gene, this activity potentiates feedback inhibition, constraining the window of DUX4 activity. The DUX gene family therefore comprises cross-regulating members of opposing function, with implications for their roles in ZGA, FSHD, and cancer. HIGHLIGHTS: Platypus sDUX is toxic and inhibits myogenic differentiation.DUXA targets overlap substantially with those of DUX4.DUXA fused to a synthetic transactivation domain acquires DUX4-like toxicity.DUXA behaves as a competitive inhibitor of DUX4.

Antagonism among DUX family members evolved from an ancestral toxic single homeodomain protein.

Double homeobox (DUX) genes are unique to eutherian mammals, expressed transiently during zygotic genome activation (ZGA) and involved in facioscapulohumeral muscular dystrophy (FSHD) and cancer when misexpressed. We evaluate the 3 human DUX genes and the ancestral single homeobox gene sDUX from the non-eutherian mammal, platypus, and find that DUX4 cytotoxicity is not shared with DUXA or DUXB, but surprisingly is shared with platypus sDUX, which binds DNA as a homodimer and activates numerous ZGA genes and long terminal repeat (LTR) elements. DUXA, although transcriptionally inactive, has DNA binding overlap with DUX4, and DUXA-VP64 activates DUX4 targets and is cytotoxic. DUXA competition antagonizes the activity of DUX4 on its target genes, including in FSHD patient cells. Since DUXA is a DUX4 target gene, this competition potentiates feedback inhibition, constraining the window of DUX4 activity. The DUX gene family therefore comprises antagonistic members of opposing function, with implications for their roles in ZGA, FSHD, and cancer.

Structural and physicochemical characteristics of wheat starch as influenced by freeze-thawed cycles and antifreeze protein from Sabina chinensis (Linn.) Ant. cv. Kaizuca leaves.

The effects of freeze-thawed cycles (FTs) and a new antifreeze protein from Sabina chinensis (Linn.) Ant. cv. Kaizuca leaves (ScAFP) on the structure and physicochemical characteristics of wheat starch were studied. The mechanical breaking exerted by ice crystals on starch granules during FTs gradually deepened, sequentially squeezing the surface (2-6 FTs), amorphous region (8 FTs) and crystalline region (10 FTs) of starch granules. These changes led to reduced thermal stability, increased retrogradation tendency, and weakened gel network structure. The addition of ScAFP retarded the damage of ice crystals on starch granule structure and crystal structure during FTs, and significantly reduced the retrogradation tendency. Compared with native starch, the hardness of freeze-thawed starch without and with added ScAFP after 10 FTs decreased by 17.85% and 9.22%, respectively, indicating ScAFP improved the gel texture properties of freeze-thawed starch. This study provides new strategies for improving the quality of frozen starch-based foods.

Effect of Kinesiology Tape on Muscle Activation of Lower Extremity and Ankle Kinesthesia in Individuals With Unilateral Chronic Ankle Instability.

Background: The purpose of the study was to determine the effect of kinesiology tape (KT) on lower limb muscle activation during computerized dynamic posturography (CDP) tasks and ankle kinesthesia in individuals with chronic ankle instability (CAI). Methods: Thirty-five men with CAI participated in this study. The experimental procedure followed a repeated measures design. Muscle activation of lower extremity and ankle kinesthesia of participants were measured using four taping treatments, namely, KT, athletic tape (AT), sham tape (ST), and no tape (NT) in a randomized order. Muscle activation was assessed using surface electromyography (sEMG) synchronized with CDP tests from seven lower extremity muscles of the unstable limb. Ankle kinesthesia was measured by using a threshold to detect the passive motion direction of the unstable ankle. Parameters were analyzed by using a one-way repeated measures ANOVA and followed by pairwise comparisons with a Bonferroni correction. Results: No significant difference was observed among different taping treatments for the majority of parameters during CDP. Except for condition 4 with open eyes, sway-referenced surface, and fixed surround in the sensory organization test (SOT), gastrocnemius medialis root mean square (RMS) was 28.19% lower in AT compared with NT (p = 0.021, 95% CI = 0.002-0.039), while gastrocnemius lateralis RMS was 20.25% lower in AT compared with KT (p = 0.038, 95% CI = 0.000-0.021). In forward-small sudden translation from motor control test (MCT), for peroneal longus (PL), RMS was 24.04% lower in KT compared with ST (p = 0.036, 95% CI = 0.000-0.018). In toes-down sudden rotation from adaption test (ADT), for PL, RMS was 23.41% lower in AT compared with ST (p = 0.015, 95% CI = 0.002-0.027). In addition, no significant difference was observed for a threshold to the detection of passive motion direction among different taping treatments. Conclusion: This study indicated that KT had minimal effect on the muscle activation of the unstable lower limb during static stance, self-initiated, and externally triggered perturbation tasks from CDP and ankle kinesthesia among individuals with CAI, suggesting that the benefit of KT was too small to be clinically worthwhile during application for CAI.

The Effect of Heterogenous Subregions in Glioblastomas on Survival Stratification: A Radiomics Analysis Using the Multimodality MRI.

Intratumor heterogeneity is partly responsible for the poor prognosis of glioblastoma (GBM) patients. In this study, we aimed to assess the effect of different heterogeneous subregions of GBM on overall survival (OS) stratification. A total of 105 GBM patients were retrospectively enrolled and divided into long-term and short-term OS groups. Four MRI sequences, including contrast-enhanced T1-weighted imaging (T1C), T1, T2, and FLAIR, were collected for each patient. Then, 4 heterogeneous subregions, i.e. the region of entire abnormality (rEA), the regions of contrast-enhanced tumor (rCET), necrosis (rNec) and edema/non-contrast-enhanced tumor (rE/nCET), were manually drawn from the 4 MRI sequences. For each subregion, 50 radiomics features were extracted. The stratification performance of 4 heterogeneous subregions, as well as the performances of 4 MRI sequences, was evaluated both alone and in combination. Our results showed that rEA was superior in stratifying long-and short-term OS. For the 4 MRI sequences used in this study, the FLAIR sequence demonstrated the best performance of survival stratification based on the manual delineation of heterogeneous subregions. Our results suggest that heterogeneous subregions of GBMs contain different prognostic information, which should be considered when investigating survival stratification in patients with GBM.

Lower extremity stiffness in habitual forefoot strikers during running on different overground surfaces.

PURPOSE: Sports surface is one of the known external factors affecting running performance and injury. To date, we have found no study that examined the lower extremity stiffness in habitual forefoot strikers running on different overground surfaces. Therefore, the objective of this study was to investigate lower extremity stiffness and relevant kinematic adjustments in habitual forefoot strikers while running on different surfaces. METHODS: Thirty-one male habitual forefoot strikers were recruited in this study. Runners were instructed to run at a speed of 3.3 m/s (±5%) on three surfaces, named synthetic rubber, concrete, and artificial grass. RESULTS: No significant differences were found in leg stiffness, vertical stiffness, and joint stiffness in the sagittal plane during running on the three surfaces ( p > 0.05). Running on artificial grass exerted a greater displacement in knee joint angle than running on synthetic rubber ( p = 0.002, 95% CI = 1.52-7.35 degrees) and concrete ( p = 0.006, 95% CI = 1.04-7.25 degrees). In the sagittal plane, peak knee moment was lower on concrete than on artificial grass ( p = 0.003, 95% CI = 0.11-0.58 Nm/kg), whereas peak ankle moment was lower on synthetic rubber than on concrete ( p < 0.001, 95% CI = 0.03-0.07 Nm/kg) and on artificial grass ( p < 0.001, 95% CI = 0.02-0.06 Nm/kg). Among the three surfaces, the maximal ground reaction forces on concrete were the lowest ( p < 0.05). CONCLUSIONS: This study indicated that running surfaces cannot influence lower extremity stiffness in habitual forefoot strikers at current running speed. Kinematic adjustments of knee and ankle, as well as ground reaction forces, may contribute to maintaining similar lower extremity stiffness.

Structure and dynamics of SARS-CoV-2 proofreading exoribonuclease ExoN.

High-fidelity replication of the large RNA genome of coronaviruses (CoVs) is mediated by a 3'-to-5' exoribonuclease (ExoN) in non-structural protein 14 (nsp14), which excises nucleotides including antiviral drugs mis-incorporated by the low-fidelity viral RNA-dependent RNA polymerase (RdRp) and has also been implicated in viral RNA recombination and resistance to innate immunity. Here we determined a 1.6-Å resolution crystal structure of SARS-CoV-2 ExoN in complex with its essential co-factor, nsp10. The structure shows a highly basic and concave surface flanking the active site, comprising several Lys residues of nsp14 and the N-terminal amino group of nsp10. Modeling suggests that this basic patch binds to the template strand of double-stranded RNA substrates to position the 3' end of the nascent strand in the ExoN active site, which is corroborated by mutational and computational analyses. Molecular dynamics simulations further show remarkable flexibility of multi-domain nsp14 and suggest that nsp10 stabilizes ExoN for substrate RNA-binding to support its exoribonuclease activity. Our high-resolution structure of the SARS-CoV-2 ExoN-nsp10 complex serves as a platform for future development of anti-coronaviral drugs or strategies to attenuate the viral virulence.