Palmitoylation of SARS-CoV-2 Envelope protein is central to virus particle formation.

The Envelope (E) protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is an integral structural protein in the virus particles. However, its role in the assembly of virions and the underlying molecular mechanisms are yet to be elucidated, including whether the function of E protein is regulated by post-translational modifications. In the present study, we report that SARS-CoV-2 E protein is palmitoylated at C40, C43, and C44 by palmitoyltransferases zDHHC3, 6, 12, 15, and 20. Mutating these three cysteines to serines (C40/43/44S) reduced the stability of E protein, decreased the interaction of E with structural proteins Spike, Membrane, and Nucleocapsid, and thereby inhibited the production of virus-like particles (VLPs) and VLP-mediated luciferase transcriptional delivery. Specifically, the C40/43/44S mutation of E protein reduced the density of VLPs. Collectively, these results demonstrate that palmitoylation of E protein is vital for its function in the assembly of SARS-CoV-2 particles.IMPORTANCEIn this study, we systematically examined the biochemistry of palmitoylation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) E protein and demonstrated that palmitoylation of SARS-CoV-2 E protein is required for virus-like particle (VLP) production and maintaining normal particle density. These results suggest that palmitoylated E protein is central for proper morphogenesis of SARS-CoV-2 VLPs in densities required for viral infectivity. This study presents a significant advancement in the understanding of how palmitoylation of viral proteins is vital for assembling SARS-CoV-2 particles and supports that palmitoyl acyltransferases can be potential therapeutic targets for the development of SARS-CoV-2 inhibitors.

Construction and validation of prognostic signature for hepatocellular carcinoma basing on hepatitis B virus related specific genes.

BACKGROUND: Hepatocellular carcinoma (HCC) is a frequent primary liver cancer, and it is one of the leading cause of cancer-related deaths. Hepatitis B virus (HBV) infection is a crucial risk factor for HCC. Thus, this study aimed to explore the prognostic role of HBV-positive HCC related specific genes in HCC. METHODS: The HCC related data were downloaded from three databases, including The Cancer Genome Atlas (TCGA), International Cancer Genome Consortium (ICGC), and Gene Expression Omnibus (GEO). Univariate Cox regression analysis and LASSO Cox regression analysis were conducted to build the Risk score. Multivariate Cox regression analysis and survival analysis determined the independent prognostic indicators. RESULTS: After cross analysis of differentially expressed genes (DEGs), we have identified 106 overlapped DEGs, which were probably HBV-positive HCC related specific genes. These 106 DEGs were significantly enriched in 213 GO terms and 8 KEGG pathways. Among that, 11 optimal genes were selected to build a Risk score, and Risk score was an independent prognostic factor for HCC. High risk HCC patients had worse OS. Moreover, five kinds of immune cells were differentially infiltrated between high and low risk HCC patients. CONCLUSION: The prognostic signature, based on HMMR, MCM6, TPX2, KIF20A, CCL20, RGS2, NUSAP1, FABP5, FZD6, PBK, and STK39, is conducive to distinguish different prognosis of HCC patients.

SGK1, a Serine/Threonine Kinase, Inhibits Prototype Foamy Virus Replication.

Foamy viruses (FVs) are complex retroviruses belonging to the Spumaretrovirinae subfamily of the Retroviridae family. In contrast to human immunodeficiency virus (HIV), another member of the Retroviridae family, FVs are nonpathogenic in their natural hosts or in experimentally infected animals. Prototype foamy virus (PFV) is the only foamy virus that can infect humans through cross-species transmission and does not show any pathogenicity after infection. Consequently, PFV is considered a safe and efficient gene transfer vector. Understanding the host proteins involved in the replication of PFV and the mechanism of interaction between the host and the virus might lead to studies to improve the efficiency of gene transfer. To date, only a few host factors have been identified that affect PFV replication. In the present study, we report that PFV infection enhances the promoter activity of SGK1 (encoding serum/glucocorticoid regulated kinase 1) via the Tas protein signaling pathway, and then upregulates the mRNA and protein levels of SGK1. Overexpression of SGK1 reduced PFV replication, whereas its depletion using small interfering RNA increased PFV replication. SGK1 inhibits PFV replication by impairing the function of the PFV Tas activation domain in a kinase-independent manner and reducing the stability of the Gag protein in a kinase-dependent manner. In addition, both human and bovine SGK1 proteins inhibit the replication of bovine foamy virus (BFV) and PFV. These findings not only improved our understanding of the function of SGK1 and its relationship with foamy viruses, but also contributed to determining the antiviral mechanism of the host. IMPORTANCE Foamy viruses can integrate into the host chromosome and are nonpathogenic in natural hosts or in experimentally infected animals. Therefore, foamy viruses are considered to be safe and efficient gene transfer vectors. Persistent infection of foamy viruses is partly caused by the restrictive effect of host factors on the virus. However, only a few cellular proteins are known to influence the replication of foamy viruses. In this study, we report that SGK1 inhibits the replication of prototype foamy virus by affecting the function of the transcription activator, Tas, and reducing the stability of the structural protein, Gag. These results will increase our understanding of the interaction between the virus and host factors, deepening our perception of host antiviral defenses and the function of SGK1, and could improve the gene transfer efficiency of foamy viruses.

Enterovirus 71 Activates GADD34 via Precursor 3CD to Promote IRES-Mediated Viral Translation.

Enterovirus 71 (EV71) is the major pathogen of hand, foot, and mouth disease. In severe cases, it can cause life-threatening neurological complications, such as aseptic meningitis and polio-like paralysis. There are no specific antiviral treatments for EV71 infections. In a previous study, the host protein growth arrest and DNA damage-inducible protein 34 (GADD34) expression was upregulated during EV71 infection determined by ribosome profiling and RNA-sequencing. Here, we investigated the interactions of host protein GADD34 and EV71 during infections. Rhabdomyosarcoma (RD) cells were infected with EV71 resulting in a significant increase in expression of GADD34 mRNA and protein. Through screening of EV71 protein we determined that the non-structural precursor protein 3CD is responsible for upregulating GADD34. EV71 3CD increased the RNA and protein levels of GADD34, while the 3CD mutant Y441S could not. 3CD upregulated GADD34 translation via the upstream open reading frame (uORF) of GADD34 5'untranslated regions (UTR). EV71 replication was attenuated by the knockdown of GADD34. The function of GADD34 to dephosphorylate eIF2α was unrelated to the upregulation of EV71 replication, but the PEST 1, 2, and 3 regions of GADD34 were required. GADD34 promoted the EV71 internal ribosome entry site (IRES) activity through the PEST repeats and affected several other viruses. Finally, GADD34 amino acids 563 to 565 interacted with 3CD, assisting GADD34 to target the EV71 IRES. Our research reveals a new mechanism by which GADD34 promotes viral IRES and how the EV71 non-structural precursor protein 3CD regulates host protein expression to support viral replication. IMPORTANCE Identification of host factors involved in viral replication is an important approach in discovering viral pathogenic mechanisms and identifying potential therapeutic targets. Previously, we screened host proteins that were upregulated by EV71 infection. Here, we report the interaction between the upregulated host protein GADD34 and EV71. EV71 non-structural precursor protein 3CD activates the RNA and protein expression of GADD34. Our study reveals that 3CD regulates the uORF of the 5'-UTR to increase GADD34 translation, providing a new explanation for how viral proteins regulate host protein expression. GADD34 is important for EV71 replication, and the key functional domains of GADD34 that promote EV71 are PEST 1, 2, and 3 regions. We report that GADD34 promotes viral IRES for the first time and this process is independent of its eIF2α phosphatase activity.

Downregulation of Hotair or LSD1 Impaired Heart Regeneration in the Neonatal Mouse.

Previous studies have shown that lysine-specific demethylase 1 (LSD1) could regulate cell cycle progression through demethylation. The 3'domain of HOX transcript antisense RNA (Hotair) combined with the LSD1/CoREST/REST complex helps LSD1 target the corresponding gene. However, its role in mice's myocardial regeneration is still unclear. The heart from neonatal mice shows strong myocardial regeneration ability, but this ability disappears 7 days after birth. Our study shows that the myocardial tissue highly expresses Hotair and Lsd1 within 1 week after birth, consistent with the myocardial regeneration time window. Knockdown Lsd1 or Hotair expression by RNA interference could inhibit myocardial regeneration and cardiomyocyte proliferation. Our results suggest that Hotair-mediated demethylation of LSD1 may play an important role in myocardial regeneration in neonatal mice.

lncRNA HOTAIR Promotes DNA Repair and Radioresistance of Breast Cancer via EZH2.

Mounting evidence shows that long noncoding RNAs play important roles in human diseases and radioresistance could be an important factor for tumor recurrence. We observed that HOX antisense intergenic RNA (HOTAIR) expression increased in invasive ductal carcinoma (IDC) tissue. The irradiation effect of HOTAIR was detected by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay, cell cycle and apoptosis analysis, and xenografts in nude mice. Western blot, RNA pulldown assay, and RNA immunoprecipitation were used for mechanistic studies. HOTAIR, upregulated in IDC of breast cancer tissue, could promote breast cancer cell proliferation by regulating cell cycle and apoptosis. Overexpression of HOTAIR promoted DNA damage repair factors KU70, KU80, DNA-PKs, and ATM expression, and these could be impeded by small molecular inhibitors of enhancer of zeste homolog 2 (EZH2). Meanwhile, we found that HOTAIR could facilitate recruitment of EZH2 to the Avian Myelocytomatosis Viral Oncogene Homolog (MYC) promoter. HOTAIR is an important modulator not only to the prognostic of breast cancer, but also a good marker for radiotherapy.

Autologous Blood Transfusion and Pringle Maneuver in Laparoscopic Segmental Hepatectomy for Benign Hepatic Neoplasms: A Retrospective Study.

Objectives: To investigate the effect of autologous blood transfusion (ABT) and Pringle maneuver (PM) on postoperative early liver function and short-term postoperative results following laparoscopic liver resection in patients with benign hepatic neoplasms. Materials and Methods: We retrospectively analyzed the clinical data for 125 consecutive patients who underwent laparoscopic segmental hepatectomy from January 2015 to May 2018 (68 in the ABT group versus 57 in the PM group). We compared patients' characteristics and intra- and postoperative short-term outcomes between the groups. Results: The 2 groups were well matched regarding patients' clinical characteristics, types of liver resection, operative time, and histopathological findings (P > .05). Median blood loss was significantly lower in the PM group versus the ABT group (200 mL versus 750 mL, respectively; P < .01), and overall complication rates were similar (n = 12 [17%] versus n = 9 [16%], respectively; P > .05). The ABT group had significantly lower mean levels of total bilirubin, indirect bilirubin, aspartate transaminase, and alanine aminotransferase on postoperative days 1 and 3 (P < .05). The ABT group had a shorter hospital stay compared with the PM group (5.8 days versus 7.7 days, respectively; P < .05) and lower hospitalization costs (55,400 ± 15,400 versus 667,000 ± 21,600 CN dollars, respectively; P < .05). Conclusions: Compared with Pringle's maneuver, laparoscopic hepatectomy with ABT promoted early recovery of liver function and reduced hospitalization costs in select patients with benign hepatic neoplasms.