Structural and functional insights into the 2'-O-methyltransferase of SARS-CoV-2.

A unique feature of coronaviruses is their utilization of self-encoded nonstructural protein 16 (nsp16), 2'-O-methyltransferase (2'-O-MTase), to cap their RNAs through ribose 2'-O-methylation modification. This process is crucial for maintaining viral genome stability, facilitating efficient translation, and enabling immune escape. Despite considerable advances in the ultrastructure of SARS-CoV-2 nsp16/nsp10, insights into its molecular mechanism have so far been limited. In this study, we systematically characterized the 2'-O-MTase activity of nsp16 in SARS-CoV-2, focusing on its dependence on nsp10 stimulation. We observed cross-reactivity between nsp16 and nsp10 in various coronaviruses due to a conserved interaction interface. However, a single residue substitution (K58T) in SARS-CoV-2 nsp10 restricted the functional activation of MERS-CoV nsp16. Furthermore, the cofactor nsp10 effectively enhanced the binding of nsp16 to the substrate RNA and the methyl donor S-adenosyl-L-methionine (SAM). Mechanistically, His-80, Lys-93, and Gly-94 of nsp10 interacted with Asp-102, Ser-105, and Asp-106 of nsp16, respectively, thereby effectively stabilizing the SAM binding pocket. Lys-43 of nsp10 interacted with Lys-38 and Gly-39 of nsp16 to dynamically regulate the RNA binding pocket and facilitate precise binding of RNA to the nsp16/nsp10 complex. By assessing the conformational epitopes of nsp16/nsp10 complex, we further determined the critical residues involved in 2'-O-MTase activity. Additionally, we utilize an in vitro biochemical platform to screen potential inhibitors targeting 2'-O-MTase activity. Overall, our results significantly enhance the understanding of viral 2'-O methylation process and mechanism, providing valuable targets for antiviral drug development.

The lethal K18-hACE2 knock-in mouse model mimicking the severe pneumonia of COVID-19 is practicable for antiviral development.

Animal models of COVID-19 facilitate the development of vaccines and antivirals against SARS-CoV-2. The efficacy of antivirals or vaccines may differ in different animal models with varied degrees of disease. Here, we introduce a mouse model expressing human angiotensin-converting enzyme 2 (ACE2). In this model, ACE2 with the human cytokeratin 18 promoter was knocked into the Hipp11 locus of C57BL/6J mouse by CRISPR - Cas9 (K18-hACE2 KI). Upon intranasal inoculation with high (3 × 105 PFU) or low (2.5 × 102 PFU) dose of SARS-CoV-2 wildtype (WT), Delta, Omicron BA.1, or Omicron BA.2 variants, all mice showed obvious infection symptoms, including weight loss, high viral loads in the lung, and interstitial pneumonia. 100% lethality was observed in K18-hACE2 KI mice infected by variants with a delay of endpoint for Delta and BA.1, and a significantly attenuated pathogenicity was observed for BA.2. The pneumonia of infected mice was accompanied by the infiltration of neutrophils and pulmonary fibrosis in the lung. Compared with K18-hACE2 Tg mice and HFH4-hACE2 Tg mice, K18-hACE2 KI mice are more susceptible to SARS-CoV-2. In the antivirals test, REGN10933 and Remdesivir had limited antiviral efficacies in K18-hACE2 KI mice upon the challenge of SARS-CoV-2 infections, while Nirmatrelvir, monoclonal antibody 4G4, and mRNA vaccines potently protected the mice from death. Our results suggest that the K18-hACE2 KI mouse model is lethal and stable for SARS-CoV-2 infection, and is practicable and stringent to antiviral development.

G-protein-coupled estrogen receptor 1 promotes peritoneal metastasis of gastric cancer through nicotinamide adenine dinucleotide kinase 1-mediated redox modulation.

Adipose tissue is the second most important site of estrogen production, where androgens are converted into estrogen by aromatase. While gastric cancer patients often develop adipocyte-rich peritoneal metastasis, the underlying mechanism remains unclear. In this study, we identified the G-protein-coupled estrogen receptor (GPER1) as a promoter of gastric cancer peritoneal metastasis. Functional in vitro studies revealed that ß-Estradiol (E2) or the GPER1 agonist G1 inhibited anoikis in gastric cancer cells. Additionally, genetic overexpression or knockout of GPER1 significantly inhibited or enhanced gastric cancer cell anoikis in vitro and peritoneal metastasis in vivo, respectively. Mechanically, GPER1 knockout disrupted the NADPH pool and increased reactive oxygen species (ROS) generation. Conversely, overexpression of GPER1 had the opposite effects. GPER1 suppressed nicotinamide adenine dinucleotide kinase 1(NADK1) ubiquitination and promoted its phosphorylation, which were responsible for the elevated expression of NADK1 at protein levels and activity, respectively. Moreover, genetic inhibition of NADK1 disrupted NADPH and redox homeostasis, leading to high levels of ROS and significant anoikis, which inhibited lung and peritoneal metastasis in cell-based xenograft models. In summary, our study suggests that inhibiting GPER1-mediated NADK1 activity and its ubiquitination may be a promising therapeutic strategy for peritoneal metastasis of gastric cancer.

NSUN2-mediated m5C modification of HBV RNA positively regulates HBV replication.

Chronic hepatitis B virus (HBV) infection is a major cause of liver cirrhosis and liver cancer, despite strong prevention and treatment efforts. The study of the epigenetic modification of HBV has become a research hotspot, including the N6-methyladenosine (m6A) modification of HBV RNA, which plays complex roles in the HBV life cycle. In addition to m6A modification, 5-methylcytosine (m5C) is another major modification of eukaryotic mRNA. In this study, we explored the roles of m5C methyltransferase and demethyltransferase in the HBV life cycle. The results showed that m5C methyltransferase NSUN2 deficiency could negatively regulate the expression of HBV while m5C demethyltransferase TET2 deficiency positively regulates the expression of HBV. Subsequently, we combined both in vitro bisulfite sequencing and high-throughput bisulfite sequencing methods to determine the distribution and stoichiometry of m5C modification in HBV RNA. Two sites: C2017 and C131 with the highest-ranking methylation rates were identified, and mutations at these two sites could lead to the decreased expression and replication of HBV, while the mutation of the "fake" m5C site had no effect. Mechanistically, NSUN2-mediated m5C modification promotes the stability of HBV RNA. In addition, compared with wild-type HepG2-NTCP cells and primary human hepatocytes, the replication level of HBV after NSUN2 knockdown decreased, and the ability of the mutant virus to infect and replicate in wild-type HepG2-NTCP cells and PHHs was substantially impaired. Similar results were found in the experiments using C57BL/6JGpt-Nsun2+/- mice. Interestingly, we also found that HBV expression and core protein promoted the endogenous expression of NSUN2, which implied a positive feedback loop. In summary, our study provides an accurate and high-resolution m5C profile of HBV RNA and reveals that NSUN2-mediated m5C modification of HBV RNA positively regulates HBV replication by maintaining RNA stability.

Pretransplant C-reactive protein as a prognostic marker in allogeneic stem cell transplantation: A PRISMA-compliant meta-analysis.

BACKGROUND: Numerous reports have explored the prognostic value of pretransplant serum C-reactive protein (CRP) in patients receiving allogeneic stem cell transplant (ASCT), but the results remain conflicting. Therefore, we performed a meta-analysis to comprehensively assess the prognostic value of pretransplant serum CRP in patients receiving ASCT. METHODS: We systematically searched eligible studies in PubMed, Embase, and Web of Science from 1999 to September 2018. The pooled hazard ratios (HRs) and their corresponding 95% CIs were used to synthetically assess the prognostic value of pre-ASCT CRP in terms of overall survival (OS), non-relapse mortality (NRM), and acute graft versus host disease (aGVHD). RESULTS: A total of 14 articles with 15 studies containing 3458 patients were included in this meta-analysis. The pooled results showed that high pre-ASCT CRP level was significantly related to worse OS (HR = 1.63; 95% CI: 1.34-1.98; P < .05), to an increased risk of NRM (HR = 2.06; 95% CI: 1.62-2.62; P < .05), and aGVHD (HR = 1.35; 95% CI: 1.07-1.71; P < .05). Additionally, sensitivity and subgroup analyses demonstrated that our pooled results were stable and reliable. CONCLUSIONS: High pre-ASCT serum CRP was significantly associated with worse OS, as well as higher risk of NRM and aGVHD. CRP may be a candidate factor of updating the existing risk scoring systems or establishing a novel risk scoring systems, which has the potential of guiding patient selection for ASCT and proceeding with risk-adapted therapeutic strategies. However, more high-quality clinical studies and basic research are required to further validate our findings in view of several limitations in our meta-analysis.

Effect of pre-transplantation serum ferritin on outcomes in patients undergoing allogeneic hematopoietic stem cell transplantation: A meta-analysis.

BACKGROUND: Pre-transplantation serum ferritin (SF) has been considered to be a potential prognostic biomarker in patients undergoing allogeneic hematopoietic stem cell transplantation (allogeneic HSCT), but this conclusion remains controversial. Thus, we performed a meta-analysis to investigate the prognostic significance of pre-transplantation SF in patients undergoing allogeneic HSCT. METHODS: We systematically searched PubMed, Embase, and Web of Science up to September 2017, and finally identified a total of 25 eligible studies with 4545 patients. RESULTS: The pooled results of our meta-analysis showed that high pre-transplantation SF was markedly related to worse overall survival (OS) [hazard ratio (HR) = 1.82; 95% confidence interval (95% CI): 1.47-2.26; P < .001], nonrelapse mortality (NRM) (HR = 2.28; 95% CI: 1.79-2.89; P < .001), and progression-free survival (PFS) (HR = 1.72; 95% CI: 1.27-2.33; P < .001). In addition, high pre-transplantation SF was closely associated with a lower incidence of chronic graft versus host disease (cGVHD) (OR = 0.74, 95% CI: 0.58-0.96; P < .05), and a higher incidence of blood stream infections (BSIs) (OR = 1.67, 95% CI: 0.93-3.01; P = .09). However, no significance relationship was found between elevated pre-transplantation SF and acute graft versus host disease (aGVHD) (OR = 1.08, 95% CI:.72-1.62; P = .70). CONCLUSION: In patients undergoing allogeneic HSCT for hematological malignancies, elevated pre-transplantation SF was significantly associated with worse OS and PFS, higher incidence of NRM and BSI, and lower incidence of cGVHD, but it had no effect on aGVHD. Considering the limitations in our meta-analysis, more prospective and homogeneous clinical studies are needed to further confirm our findings.

Donor liver steatosis: A risk factor for early new-onset diabetes after liver transplantation.

AIMS/INTRODUCTION: To investigate whether donor liver steatosis increases the incidence of new-onset diabetes after transplantation (NODAT) in liver transplant recipients. MATERIALS AND METHODS: We retrospectively analyzed liver transplant recipients at Zhongshan Hospital, Shanghai, China, from April 2001 to December 2014. The final analysis involved 763 patients. The cumulative incidence of NODAT at 1, 3, 5 and 10 years after liver transplantation was investigated. Furthermore, according to the findings of donor liver biopsy before transplantation, patients were divided into steatotic and non-steatotic donor liver groups, and NODAT incidence was compared between these groups. Multivariate Cox regression was used to explore the risk factors for NODAT in the patients. RESULTS: Of the 763 donors, 309 (40.5%) had liver steatosis. At the end of follow up, 130 (42.1%) patients in the steatotic donor liver group developed NODAT, an incidence that exceeded that in the non-steatotic donor liver group (P = 0.001). The cumulative incidence of NODAT among all patients at 1, 3, 5, and 10 years after transplantation was 33, 43, 50 and 56%, respectively. The cumulative incidences of NODAT at 1, 3, 5 and 10 years in the steatotic donor liver group were significantly higher than those in the non-steatotic donor liver group (P = 0.003). Multivariate Cox regression analyses showed that donor liver steatosis was an independent risk factor for NODAT among liver transplant recipients, after other potential risk factors were adjusted for (hazard ratio 1.774, 95% confidence interval: 1.025-3.073; P = 0.041). CONCLUSIONS: Donor liver steatosis increases NODAT incidence among liver transplant recipients.

New-onset diabetes after liver transplantation and its impact on complications and patient survival.

BACKGROUND: The aim of the present study was to investigate the incidence and risk factors of new-onset diabetes after transplantation (NODAT) in liver transplant recipients and the influence of NODAT on complications and long-term patient survival. METHODS: We examined 438 patients who underwent liver transplantation between April 2001 and December 2008 and were not diabetic before transplantation. RESULTS: The mean (± SD) follow-up duration was 2.46 ± 1.62 years. The incidence of NODAT 3, 6, 9, 12, 36, and 60 months after transplantation was 44.24%, 25.59%, 23.08%, 25.17%, 17.86%, and 18.18%, respectively. Multifactor analysis indicated that preoperative fasting plasma glucose (FPG) levels and donor liver steatosis were independent risk factors for NODAT, whereas administration of an interleukin-2 receptor (IL-2R) antagonist reduced the risk of NODAT. Compared with the no NODAT group (N-NODAT), the NODAT group had a higher rate of sepsis and chronic renal insufficiency. Mean survival was significantly longer in the N-NODAT than NODAT group. Cox regression analysis showed that pre- and/or postoperative FPG levels, tumor recurrence or metastasis, and renal insufficiency after liver transplantation were independent risk factors of mortality. Pulmonary infection or multisystem failure were specific causes of death in the NODAT group, whereas patients in both groups died primarily from tumor relapse or metastasis. CONCLUSIONS: Preoperative FPG levels and donor liver steatosis were independent risk factors for NODAT, whereas administration of an IL-2R antagonist reduced the risk of NODAT. Patients with NODAT had reduced survival and an increased incidence of sepsis and chronic renal insufficiency. Significant causes of death in the NODAT group were pulmonary infection and multisystem failure.

Curcumol suppresses RANKL-induced osteoclast formation by attenuating the JNK signaling pathway.

Osteoclasts, derived from hemopoietic progenitors of the monocyte/macrophage lineage, have a unique role in bone resorption, and are considered a potential therapeutic target in the treatment of such pathologic bone diseases as osteoporosis, rheumatoid arthritis, and periodontitis. In the present study, we demonstrate that curcumol, one of the major components of the essential oil of Rhizoma Curcumae, exhibits an inhibitory effect on receptor activator of nuclear factor kappaB ligand (RANKL)-induced osteoclast differentiation with both bone marrow-derived macrophages and RAW264.7 cells in a dose-dependent manner. In addition, RANKL-induced mRNA expression of osteoclast-specific genes, such as tartrate-resistant acid phosphatase, calcitonin receptor, and cathepsin K, is prominently reduced in the presence of curcumol. Furthermore, the molecular mechanism of action was investigated, and curcumol inhibited osteoclastogenesis by specifically impairing RANKL-induced c-Jun N-terminal kinase (JNK)/activator protein-1 (AP-1) signaling, which was further identified in rescue studies by means of anisomycin, a JNK signaling-specific activator. Taken together, these findings suggest that curcumol suppresses RANKL-induced osteoclast differentiation through the JNK/AP-1 signaling pathway, and may be useful as a therapeutic treatment for bone resorption-associated diseases.