TRIM26 is a critical host factor for HCV replication and contributes to host tropism

The application of CRISPR/Cas9-based genome-wide screening to disease research

High-throughput genetic screening serves as an indispensable approach for deciphering gene functions and the intricate relationships between phenotypes and genotypes. The CRISPR/Cas9 system, with its ability to precisely edit genomes on a large scale, has revolutionized the field by enabling the construction of comprehensive genomic libraries. This technology has become a cornerstone for genome-wide screenings in disease research. This review offers a comprehensive examination of how CRISPR/Cas9-based genetic screening has been leveraged to uncover genes that play a role in disease mechanisms, focusing on areas such as cancer development and viral replication processes. The insights presented in this review hold promise for the development of novel therapeutic strategies and precision medicine approaches.

Cytoskeletal Vimentin Directs Cell-Cell Transmission of Hepatitis C Virus

Hepatitis C virus (HCV) is a major human pathogen causing liver diseases. Although direct-acting antiviral agents effectively inhibit HCV infection, cell-cell transmission remains a critical venue for HCV persistence in vivo. However, the underlying mechanism of how HCV spreads intercellularly remains elusive. Here, we demonstrated that vimentin, a host intermediate filaments protein, is dispensable for HCV infection in cell models but essential for simulated in vivo infection in differentiated hepatocytes. Genetic removal of vimentin markedly and specifically disrupts HCV cell-cell transmission without influencing cell-free infection. Through mutual co-immunoprecipitation screening, we identified that the N-terminal 1-95 amino acids of vimentin exclusively interact with the HCV envelope protein E1. Introducing either full-length or head region of vimentin is capable of restoring the cell-cell transmission deficiency in vimentin-knockout cells. Moreover, we showed that it is vimentin on the plasma membrane of recipient cells that orchestrates HCV cell-cell transmission. Consequently, vimentin antibody, either applied individually or in combination with HCV neutralizing antibody, exerts pronounced inhibition of HCV cell-cell transmission. Together, the results unveil an unrecognized function of vimentin as a unique venue dominating viral transmission, providing novel insights into propelling advancements in vimentin-targeted anti-HCV therapies.

Mechanistic Role of TRIM26 in Viral Infection and Host Defense

Tripartite motif protein 26 (TRIM26) is an E3 ubiquitin ligase and a member of the TRIM family. Similar to other TRIM proteins, TRIM26 consists of three domains, collectively termed RBCC: a Really Interesting New Gene (RING) domain, one B-Box domain, and a C terminal domain consisting of a PRY/SPRY domain. The PRY/SPRY domain exhibits relatively higher conservation compared with the RING and B-Box domains, suggesting potentially similar roles across TRIM26 proteins from various species. TRIM26 either directly interacts with viral proteins or modulates immune responses to engage with a viral infection, serving as either a protective or detrimental host factor depending on the circumvent of the viral infection. The present review focuses on understanding the mechanisms of TRIM26 during viral infection and its potential future applications.

CRISPR/Cas9 screens identify key host factors that enhance rotavirus reverse genetics efficacy and vaccine production

Rotaviruses pose a significant threat to young children. To identify novel pro- and anti-rotavirus host factors, we performed genome-wide CRISPR/Cas9 screens using rhesus rotavirus and African green monkey cells. Genetic deletion of either SERPINB1 or TMEM236, the top two antiviral factors, in MA104 cells increased virus titers in a rotavirus strain independent manner. Using this information, we optimized the existing rotavirus reverse genetics systems by combining SERPINB1 knockout MA104 cells with a C3P3-G3 helper plasmid. We improved the recovery efficiency and rescued several low-titer rotavirus reporter and mutant strains that prove difficult to rescue otherwise. Furthermore, we demonstrate that TMEM236 knockout in Vero cells supported higher yields of two live-attenuated rotavirus vaccine strains than the parental cell line and represents a more robust vaccine-producing cell substrate. Collectively, we developed a third-generation optimized rotavirus reverse genetics system and generated gene-edited Vero cells as a new substrate for improving rotavirus vaccine production.

The Role of Tripartite Motif Family Proteins in Chronic Liver Diseases: Molecular Mechanisms and Therapeutic Potential

The worldwide impact of liver diseases is increasing steadily, with a consistent upswing evidenced in incidence and mortality rates. Chronic liver diseases (CLDs) refer to the liver function's progressive deterioration exceeding six months, which includes abnormal clotting factors, detoxification failure, and hepatic cholestasis. The most common etiologies of CLDs are mainly composed of chronic viral hepatitis, MAFLD/MASH, alcoholic liver disease, and genetic factors, which induce inflammation and harm to the liver, ultimately resulting in cirrhosis, the irreversible final stage of CLDs. The latest research has shown that tripartite motif family proteins (TRIMs) function as E3 ligases, which participate in the progression of CLDs by regulating gene and protein expression levels through post-translational modification. In this review, our objective is to clarify the molecular mechanisms and potential therapeutic targets of TRIMs in CLDs and provide insights for therapy guidelines and future research.

HCV 5-Methylcytosine Enhances Viral RNA Replication through Interaction with m5C Reader YBX1

Hepatitis C virus (HCV) is a positive-stranded RNA virus that mainly causes chronic hepatitis, cirrhosis and hepatocellular carcinoma. Recently we confirmed m5C modifications within NS5A gene of HCV RNA genome. However, the roles of the m5C modification and its interaction with host proteins in regulating HCV's life cycle, remain unexplored. Here, we demonstrate that HCV infection enhances the expression of the host m5C reader YBX1 through the transcription factor MAX. YBX1 acts as an m5C reader, recognizing the m5C-modified NS5A C7525 site in the HCV RNA genome and significantly enhancing HCV RNA stability. This m5C-modification is also required for YBX1 colocalization with lipid droplets and HCV Core protein. Moreover, YBX1 facilitates HCV RNA replication, as well as viral assembly/budding. The tryptophan residue at position 65 (W65) of YBX1 is critical for these functions. Knockout of YBX1 or the application of YBX1 inhibitor SU056 suppresses HCV RNA replication and viral protein translation. To our knowledge, this is the first report demonstrating that the interaction between host m5C reader YBX1 and HCV RNA m5C methylation facilitates viral replication. Therefore, hepatic-YBX1 knockdown holds promise as a potential host-directed strategy for HCV therapy.

TRIM26 facilitates PRV infection through NDP52-mediated autophagic degradation of MAVS

Pseudorabies virus (PRV) has evolved multiple strategies to evade host antiviral responses to benefit virus replication and establish persistent infection. Recently, tripartite motif 26 (TRIM26), a TRIM family protein, has been shown to be involved in a broad range of biological processes involved in innate immunity, especially in regulating viral infection. Herein, we found that the expression of TRIM26 was significantly induced after PRV infection. Surprisingly, the overexpression of TRIM26 promoted PRV production, while the depletion of this protein inhibited virus replication, suggesting that TRIM26 could positively regulate PRV infection. Further analysis revealed that TRIM26 negatively regulates the innate immune response by targeting the RIG-I-triggered type I interferon signalling pathway. TRIM26 was physically associated with MAVS independent of viral infection and reduced MAVS expression. Mechanistically, we found that NDP52 interacted with both TRIM26 and MAVS and that TRIM26-induced MAVS degradation was almost entirely blocked in NDP52-knockdown cells, demonstrating that TRIM26 degrades MAVS through NDP52-mediated selective autophagy. Our results reveal a novel mechanism by which PRV escapes host antiviral innate immunity and provide insights into the crosstalk among virus infection, autophagy, and the innate immune response.

Snakehead vesiculovirus hijacks SH3RF1 for replication via mediating K63-linked ubiquitination at K264 of the phosphoprotein

Snakehead vesiculovirus (SHVV) is a type of rhabdovirus that causes serious economic losses in snakehead fish culture in China. However, no specific antiviral drugs or vaccines are currently available for SHVV infection. In this study, 4D label-free ubiquitome analysis of SHVV-infected cells revealed dozens of ubiquitinated sites on the five SHVV proteins. We focused on investigating the ubiquitination of phosphoprotein (P), a viral polymerase co-factor involved in viral replication. SHVV-P was proved to be ubiquitinated via K63-linked ubiquitination at lysine 264 (K264). Overexpression of wild-type P, but not its K264R mutant, facilitated SHVV replication, indicating that K264 ubiquitination of the P protein is critical for SHVV replication. RNAi screening of 26 cellular E3 ubiquitin ligases identified five pro-viral factors for SHVV replication, including macrophage erythroblast attacher (MAEA), TNF receptor-associated factor 7 (TRAF7), and SH3 domain-containing ring finger protein 1 (SH3RF1), which interacted with and mediated ubiquitination of SHVV P. TRAF7 and SH3RF1, but not MAEA, mediated K63-linked ubiquitination of SHVV P, while only SH3RF1 mediated K264 ubiquitination of SHVV P. Besides, overexpression of SH3RF1 promoted SHVV replication and maintained the stability of SHVV P. In summary, SH3RF1 mediated K63-linked ubiquitination of SHVV P at K264 to facilitate SHVV replication, providing targets for developing anti-SHVV drugs and live-attenuated SHVV vaccines. Our study provides novel insights into the role of P protein in the replication of single-stranded, negative-sense RNA viruses.

The Multifunction of TRIM26: From Immune Regulation to Oncology

Ubiquitination, a crucial post-translational modification, plays a role in nearly all physiological processes. Its functional execution depends on a series of catalytic reactions involving numerous proteases. TRIM26, a protein belonging to the TRIM family, exhibits E3 ubiquitin ligase activity because of its RING structural domain, and is present in diverse cell lineages. Over the last few decades, TRIM26 has been documented to engage in numerous physiological and pathological processes as a controller, demonstrating a diverse array of biological roles. Despite the growing research interest in TRIM26, there has been limited attention given to examining the protein's structure and function in existing reviews. This review begins with a concise overview of the composition and positioning of TRIM26 and then proceeds to examine its roles in immune response, viral invasion, and inflammatory processes. Simultaneously, we demonstrate the contribution of TRIM26 to the progression of various diseases, encompassing numerous malignancies and neurologic conditions. Finally, we have investigated the potential areas for future research on TRIM26.

TRIM26 alleviates fatal immunopathology by regulating inflammatory neutrophil infiltration during Candida infection

Fungal infections have emerged as a major concern among immunocompromised patients, causing approximately 2 million deaths each year worldwide. However, the regulatory mechanisms underlying antifungal immunity remain elusive and require further investigation. The E3 ligase Trim26 belongs to the tripartite motif (Trim) protein family, which is involved in various biological processes, including cell proliferation, antiviral innate immunity, and inflammatory responses. Herein, we report that Trim26 exerts protective antifungal immune functions after fungal infection. Trim26-deficient mice are more susceptible to fungemia than their wild-type counterparts. Mechanistically, Trim26 restricts inflammatory neutrophils infiltration and limits proinflammatory cytokine production, which can attenuate kidney fungal load and renal damage during Candida infection. Trim26-deficient neutrophils showed higher proinflammatory cytokine expression and impaired fungicidal activity. We further demonstrated that excessive neutrophils infiltration in the kidney was because of the increased production of chemokines CXCL1 and CXCL2, which are mainly synthesized in the macrophages or dendritic cells of Trim26-deficient mice after Candida albicans infections. Together, our study findings unraveled the vital role of Trim26 in regulating antifungal immunity through the regulation of inflammatory neutrophils infiltration and proinflammatory cytokine and chemokine expression during candidiasis.

CRISPR-Cas system to discover host-virus interactions in Flaviviridae

The Flaviviridae virus family members cause severe human diseases and are responsible for considerable mortality and morbidity worldwide. Therefore, researchers have conducted genetic screens to enhance insight into viral dependency and develop potential anti-viral strategies to treat and prevent these infections. The host factors identified by the clustered regularly interspaced short palindromic repeats (CRISPR) system can be potential targets for drug development. Meanwhile, CRISPR technology can be efficiently used to treat viral diseases as it targets both DNA and RNA. This paper discusses the host factors related to the life cycle of viruses of this family that were recently discovered using the CRISPR system. It also explores the role of immune factors and recent advances in gene editing in treating flavivirus-related diseases. The ever-increasing advancements of this technology may promise new therapeutic approaches with unique capabilities, surpassing the traditional methods of drug production and treatment.

The E3 ligase TRIM26 suppresses ferroptosis through catalyzing K63-linked ubiquitination of GPX4 in glioma

The selenium-containing enzyme GPX4 moonlights as a central regulator of ferroptosis, an iron-dependent, nonapoptotic form of regulated cell death caused by lipid peroxidation. Yet, little is known about the mechanisms underlying the regulation of its post-transcriptional modifications. Here, we identify the tripartite motif-containing protein TRIM26 as an E3 ubiquitin ligase of GPX4. TRIM26 directly interacts with GPX4 through its Ring domain and catalyzes the ubiquitination of GPX4 at K107 and K117, which promotes the switch in polyubiquitination of GPX4 from K48 to K63, thus enhancing GPX4 protein stability. Moreover, PLK1-mediated S127 phosphorylation of TRIM26 enhances the interaction between TRIM26 and GPX4. Inhibition of TRIM26 phosphorylation causes a reduction in GPX4 K63-linked polyubiquitination and diminishes GPX4 protein levels in tumor cells. Further investigation revealed that TRIM26 is overexpressed in glioma cells. TRIM26 silencing dramatically impedes ferroptosis resistance and tumorigenesis in glioma in vivo and in vitro. Clinically, TRIM26 expression shows a direct correlation with GPX4 and PLK1 levels in glioma samples and is associated with poor outcome in patients with glioma. Collectively, these findings define the role of GPX4 K63-linked polyubiquitination in ferroptosis and suggest a potential strategy for glioma treatment.

Genome-wide CRISPR screens and their applications in infectious disease

Inactivation or targeted disruption of a gene provides clues to assess the function of the gene in many cellular processes. Knockdown or knocking out a gene has been widely used for this purpose. However, recently CRISPR mediated genome editing has taken over the knockout/knockdown system with more precision. CRISPR technique has enabled us to perform targeted mutagenesis or genome editing to address questions in fundamental biology to biomedical research. Its application is wide in understanding the role of genes in the disease process, and response to therapy in cancer, metabolic disorders, or infectious disease. In this article, we have focused on infectious disease and how genome-wide CRISPR screens have enabled us to identify host factors involved in the process of infection. Understanding the biology of the host-pathogen interaction is of immense importance in planning host-directed therapy to improve better management of the disease. Genome-wide CRISPR screens provide strong mechanistic ways to identify the host dependency factors involved in various infections. We presented insights into genome-wide CRISPR screens conducted in the context of infectious diseases both viral and bacterial that led to better understanding of host-pathogen interactions and immune networks. We have discussed the advancement of knowledge pertaining to influenza virus, different hepatitis viruses, HIV, most recent SARS CoV2 and few more. Among bacterial diseases, we have focused on infection with life threatening Mycobacteria, Salmonella, S. aureus, etc. It appears that the CRISPR technique can be applied universally to multiple infectious disease models to unravel the role of known or novel host factors.

Discovery of a fused bicyclic derivative of 4-hydroxypyrrolidine and imidazolidinone as a new anti-HCV agent

Hepatitis C virus (HCV) infection causes severe liver diseases and remains a major global public health concern. Current direct-acting antiviral (DAA)-based therapies that target viral proteins involving HCV genome replication are effective, however a minority of patients still fail to cure HCV, rendering a window to develop additional antivirals particularly targeting host functions involving in HCV infection. Here, we utilized the HCV infection cell culture system (HCVcc) to screen in-house compounds bearing host-interacting preferred scaffold for the antiviral activity. Compound HXL-10, a novel fused bicyclic derivative of pyrrolidine and imidazolidinone, was identified as a potent anti-HCV agent with a low cytotoxicity and high specificity. Mechanistic studies showed that HXL-10 neither displayed a virucidal effect nor inhibited HCV genomic RNA replication. Instead, HXL-10 might inhibit HCV assembly by targeting host functions. In summary, we developed a novel anti-HCV agent that may potentially offer additive benefits to the current anti-HCV DDA.

Emerging and potential use of CRISPR in human liver disease

CRISPR is a gene editing tool adapted from naturally occurring defense systems from bacteria. It is a technology that is revolutionizing the interrogation of gene functions in driving liver disease, especially through genetic screens and by facilitating animal knockout and knockin models. It is being used in models of liver disease to identify which genes are critical for liver pathology, especially in genetic liver disease, hepatitis, and in cancer initiation and progression. It holds tremendous promise in treating human diseases directly by editing DNA. It could disable gene function in the case of expression of a maladaptive protein, such as blocking transthyretin as a therapy for amyloidosis, or to correct gene defects, such as restoring the normal functions of liver enzymes fumarylacetoacetate hydrolase or alpha-1 antitrypsin. It is also being studied for treatment of hepatitis B infection. CRISPR is an exciting, evolving technology that is facilitating gene characterization and discovery in liver disease and holds the potential to treat liver diseases safely and permanently.

TRIM26 positively affects hepatitis B virus replication by inhibiting proteasome-dependent degradation of viral core protein

Chronic hepatitis B virus (HBV) infection is a major medical concern worldwide. Current treatments for HBV infection effectively inhibit virus replication; however, these treatments cannot cure HBV and novel treatment-strategies should be necessary. In this study, we identified tripartite motif-containing protein 26 (TRIM26) could be a supportive factor for HBV replication. Small interfering RNA-mediated TRIM26 knockdown (KD) modestly attenuated HBV replication in human hepatocytes. Endogenous TRIM26 physically interacted with HBV core protein (HBc), but not polymerase and HBx, through the TRIM26 SPRY domain. Unexpectedly, TRIM26 inhibited HBc ubiquitination even though TRIM26 is an E3 ligase. HBc was degraded by TRIM26 KD in Huh-7 cells, whereas the reduction was restored by a proteasome inhibitor. RING domain-deleted TRIM26 mutant (TRIM26ΔR), a dominant negative form of TRIM26, sequestered TRIM26 from HBc, resulting in promoting HBc degradation. Taking together, this study demonstrated that HBV utilizes TRIM26 to avoid the proteasome-dependent HBc degradation. The interaction between TRIM26 and HBc might be a novel therapeutic target against HBV infection.

Mouse Liver-Expressed Shiftless Is an Evolutionarily Conserved Antiviral Effector Restricting Human and Murine Hepaciviruses

Mice are refractory to infection with human-tropic hepatitis C virus (HCV), although distantly related rodent hepaciviruses (RHV) circulate in wild rodents. To investigate whether liver intrinsic host factors can exhibit broad restriction against these distantly related hepaciviruses, we focused on Shiftless (Shfl), an interferon (IFN)-regulated gene (IRG) which restricts HCV in humans. Unusually, and in contrast to selected classical IRGs, human and mouse SHFL orthologues (hSHFL and mSHFL, respectively) were highly expressed in hepatocytes in the absence of viral infection, weakly induced by IFN, and highly conserved at the amino acid level (>95%). Replication of both HCV and RHV subgenomic replicons was suppressed by ectopic expression of mSHFL in human or rodent hepatoma cell lines. Gene editing of endogenous mShfl in mouse liver tumor cells increased HCV replication and virion production. Colocalization of mSHFL protein with viral double-stranded RNA (dsRNA) intermediates was confirmed and could be ablated by mutational disruption of the SHFL zinc finger domain, concomitant with a loss of antiviral activity. In summary, these data point to an evolutionarily conserved function for this gene in humans and rodents: SHFL is an ancient antiviral effector which targets distantly related hepaciviruses via restriction of viral RNA replication. IMPORTANCE Viruses have evolved ways to evade or blunt innate cellular antiviral mechanisms within their cognate host species. However, these adaptations may fail when viruses infect new species and can therefore limit cross-species transmission. This may also prevent development of animal models for human-pathogenic viruses. HCV shows a narrow species tropism likely due to distinct human host factor usage and innate antiviral defenses limiting infection of nonhuman liver cells. Interferon (IFN)-regulated genes (IRGs) partially inhibit HCV infection of human cells by diverse mechanisms. Here, we show that mouse Shiftless (mSHFL), a protein that interferes with HCV replication factories, inhibits HCV replication and infection in human and mouse liver cells. We further report that the zinc finger domain of SHFL is important for viral restriction. These findings implicate mSHFL as a host factor that impairs HCV infection of mice and provide guidance for development of HCV animal models needed for vaccine development.

Zebrafish maoc1 Attenuates Spring Viremia of Carp Virus Propagation by Promoting Autophagy-Lysosome-Dependent Degradation of Viral Phosphoprotein

Spring viremia of carp virus (SVCV) is the causative agent of spring viremia of carp (SVC), an important infectious disease that causes high mortality in aquaculture cyprinids. How the host defends against SVCV infection and the underlying mechanisms are still elusive. In this study, we identify that a novel gene named maoc1 is induced by SVCV infection. maoc1-deficient zebrafish are more susceptible to SVCV infection, with higher virus replication and antiviral gene induction. Further assays indicate that maoc1 interacts with the P protein of SVCV to trigger P protein degradation through the autophagy-lysosomal pathway, leading to the restriction of SVCV propagation. These findings reveal a unique zebrafish defense machinery in response to SVCV infection. IMPORTANCE SVCV P protein plays an essential role in the virus replication and viral immune evasion process. Here, we identify maoc1 as a novel SVCV-inducible gene and demonstrate its antiviral capacity through attenuating SVCV replication, by directly binding to P protein and mediating its degradation via the autophagy-lysosomal pathway. Therefore, this study not only reveals an essential role of maoc1 in fighting against SVCV infection but also demonstrates an unusual host defense mechanism in response to invading viruses.

Insights into Synonymous Codon Usage Bias in Hepatitis C Virus and Its Adaptation to Hosts

Hepatitis C virus (HCV) is enveloped RNA virus, encoding for a polyprotein that is processed by cellular proteases. The virus is responsible for liver cirrhosis, allograft rejection, and human hepatocellular carcinoma. Based on studies including compositional analysis, odds ratio analysis, parity analysis, skew analysis, relative synonymous codon usage, codon bias, and protein properties, it was evident that codon usage bias in HCV is dependent upon the nucleotide composition. Codon context analysis revealed CTC-CTG as a preferred codon pair. While CGA and CGT codons were rare, none of the codons were rare in HCV-like viruses envisaged in the present study. Many of the preferred codon pairs were valine amino acid-initiated, which possibly infers viral infectivity; hence the role of selection forces appears to act on the HCV genome, which was further validated by neutrality analysis where selection accounted for 87.28%, while mutation accounted for 12.72% force shaping codon usage. Furthermore, codon usage was correlated with the length of the genome. HCV viruses prefer valine-initiated codon pairs, while HCV-like viruses prefer alanine-initiated codon pairs. The HCV host range is very narrow and is confined to only humans and chimpanzees. Based on indices including codon usage correlation analysis, similarity index, and relative codon deoptimization index, it is evident in the study that the chimpanzee is the primary host of the virus. The present study helped elucidate the preferred host for HCV. The information presented in the study paved the way for generating an attenuated vaccine candidate through viral recoding, with finely tuned nucleotide composition and a perfect balance of preferred and rare codons.

Barriers to hepatitis C virus infection in mice

Hepatitis C virus (HCV) is unable to infect mice, a fact that has severely limited their use as small-animal models for HCV pathogenesis and as tools for HCV vaccine development. HCV is blocked at various stages of its life cycle in mouse cells, due to incompatibility with host factors, the presence of dominant restriction factors, and effective immune responses. Molecular mechanisms for several such blocks have been characterized. The stepwise understanding of these limitations in mice will enable the development of an immunocompetent mouse that can fully support HCV infection and exhibit disease similar to that of infected humans.

TRIM proteins in hepatocellular carcinoma

The tripartite motif (TRIM) protein family is a highly conserved group of E3 ligases with 77 members known in the human, most of which consist of a RING-finger domain, one or two B-box domains, and a coiled-coil domain. Generally, TRIM proteins function as E3 ligases to facilitate specific proteasomal degradation of target proteins. In addition, E3 ligase independent functions of TRIM protein were also reported. In hepatocellular carcinoma, expressions of TRIM proteins are both regulated by genetic and epigenetic mechanisms. TRIM proteins regulate multiple biological activities and signaling cascades. And TRIM proteins influence hallmarks of HCC. This review systematically demonstrates the versatile roles of TRIM proteins in HCC and helps us better understand the molecular mechanism of the development and progression of HCC.

TRIM26 inhibits hepatitis B virus replication by promoting HBx degradation and TRIM26 genetic polymorphism predicts PegIFNα treatment response of HBeAg-positive chronic hepatitis B Patients

BACKGROUND

Hepatitis B virus (HBV) infection is a serious global health burden. TRIM26 has been reported to affect hepatitis C virus replication.

AIMS

To manifest the role of TRIM26 on HBV replication and explore if there are single-nucleotide polymorphisms (SNPs) in TRIM26 associated with response to pegylated interferon-alpha (PegIFNα) treatment in patients with chronic hepatitis B (CHB).

METHODS

We investigated the effect and mechanism of TRIM26 on HBV replication in vitro. The association between SNPs in TRIM26 and PegIFNα treatment response was evaluated in two independent cohorts including 238 and 707 patients with HBeAg-positive CHB.

RESULTS

Knockdown of TRIM26 increased, while overexpression of TRIM26 inhibited, HBV replication. Co-immunoprecipitation assays and immunofluorescence showed that TRIM26 interacted and co-localised with HBx. Co-transfection of HBx-HIS and TRIM26-FLAG plasmids in Huh7 cells showed that TRIM26 inhibited the expression of HBx. Furthermore, TRIM26 inhibited HBV replication by mediating HBx ubiquitination degradation, and TRIM26 SPRY domain was responsible for the interaction and degradation of HBx. Besides, IFN increased TRIM26 expression. TRIM26 rs116806878 was associated with response to PegIFNα in two CHB cohorts. Moreover, a polygenic score integrating TRIM26 rs116806878, STAT4 rs7574865 and CFB rs12614 (previously reported to be associated with response to PegIFNα) was related to response to PegIFNα in CHB.

CONCLUSIONS

TRIM26 inhibits HBV replication; IFN promotes TRIM26 expression. TRIM26 exerts an inhibitory effect on HBx by promoting ubiquitin-mediated degradation of HBx. Furthermore, TRIM26 rs116806878 is a potential predictive biomarker of response to PegIFNα in patients with CHB.

Dual-Role Ubiquitination Regulation Shuttling the Entire Life Cycle of the Flaviviridae

Ubiquitination is a reversible protein post-translational modification that regulates various pivotal physiological and pathological processes in all eukaryotes. Recently, the antiviral immune response is enhanced by the regulation of ubiquitination. Intriguingly, Flaviviridae viruses can ingeniously hijack the ubiquitination system to help them survive, which has become a hot topic among worldwide researchers. The Flaviviridae family members, such as HCV and CSFV, can cause serious diseases of humans and animals around the world. The multiple roles of ubiquitination involved in the life cycle of Flaviviridae family would open new sight for future development of antiviral tactic. Here, we discuss recent advances with regard to functional roles of ubiquitination and some ubiquitin-like modifications in the life cycle of Flaviviridae infection, shedding new light on the antiviral mechanism research and therapeutic drug development.

Gene editing and its applications in biomedicine

The steady progress in genome editing, especially genome editing based on the use of clustered regularly interspaced short palindromic repeats (CRISPR) and programmable nucleases to make precise modifications to genetic material, has provided enormous opportunities to advance biomedical research and promote human health. The application of these technologies in basic biomedical research has yielded significant advances in identifying and studying key molecular targets relevant to human diseases and their treatment. The clinical translation of genome editing techniques offers unprecedented biomedical engineering capabilities in the diagnosis, prevention, and treatment of disease or disability. Here, we provide a general summary of emerging biomedical applications of genome editing, including open challenges. We also summarize the tools of genome editing and the insights derived from their applications, hoping to accelerate new discoveries and therapies in biomedicine.

Pseudotyped lentiviral vectors: Ready for translation into targeted cancer gene therapy?

Gene therapy holds great promise for curing cancer by editing the deleterious genes of tumor cells, but the lack of vector systems for efficient delivery of genetic material into specific tumor sites in vivo has limited its full therapeutic potential in cancer gene therapy. Over the past two decades, increasing studies have shown that lentiviral vectors (LVs) modified with different glycoproteins from a donating virus, a process referred to as pseudotyping, have altered tropism and display cell-type specificity in transduction, leading to selective tumor cell killing. This feature of LVs together with their ability to enable high efficient gene delivery in dividing and non-dividing mammalian cells in vivo make them to be attractive tools in future cancer gene therapy. This review is intended to summarize the status quo of some typical pseudotypings of LVs and their applications in basic anti-cancer studies across many malignancies. The opportunities of translating pseudotyped LVs into clinic use in cancer therapy have also been discussed.

TRIM26-mediated degradation of nucleocapsid protein limits porcine reproductive and respiratory syndrome virus-2 infection

Porcine reproductive and respiratory syndrome (PRRS), caused by PRRSV, has ranked among the most economically important veterinary infectious diseases globally. Recently, tripartite motif (TRIMs) family members have arisen as novel restriction factors in antiviral immunity. Noteworthy, TRIM26 was reported as a binding partner of IRF3, TBK1, TAB1, and NEMO, yet its role in virus infection remains controversial. Herein, we showed that TRIM26 bound N protein by the C-terminal PRY/SPRY domain. Moreover, ectopic expression of TRIM26 impaired PRRSV replication and induced degradation of N protein. The anti-PRRSV activity was independent of the nuclear localization signal (NLS). Instead, deletion of the RING domain, or the PRY/SPRY portion, abrogated the antiviral function. Finally, siRNA depletion of TRIM26 resulted in enhanced production of viral RNA and virus yield in porcine alveolar macrophages (PAMs) after PRRSV infection. Overexpression of an RNAi-resistant TRIM26 rescue-plasmid led to the acquisition of PRRSV restriction in TRIM26-knockdown cells. Together, these data add TRIM26 as a potential target for drug design against PRRSV.

Targeting Aryl Hydrocarbon Receptor Signaling Enhances Type I Interferon-Independent Resistance to Herpes Simplex Virus

The aryl hydrocarbon receptor (AHR) is a ligand-activated transcript factor that plays an important role in regulating immunity and cell differentiation. However, its role in cell-autonomous antiviral resistance has not been fully elucidated. Here, we show that interruption of AHR signaling in human cells by a chemical antagonist or genetic targeting led to significant reductions in the replication of herpes simplex virus 1 (HSV-1) and cytomegalovirus (CMV), revealing an unexpected proviral function of AHR. Interestingly, the enhanced viral control in the absence of AHR is independent of type I interferon (IFN) signaling. Together, these results reveal a previously unknown function of AHR in promoting viral replication in vitro and suggest a potential intervention point for treating viral disease. IMPORTANCE This study describes how a virus might utilize host aryl hydrocarbon receptor signaling to promote its replication, even in the presence of type I interferons.

Emerging Roles of MHC Class I Region-Encoded E3 Ubiquitin Ligases in Innate Immunity

The major histocompatibility complex (MHC) class I (MHC-I) region contains a multitude of genes relevant to immune response. Multiple E3 ubiquitin ligase genes, including tripartite motif 10 (TRIM10), TRIM15, TRIM26, TRIM27, TRIM31, TRIM38, TRIM39, TRIM40, and RING finger protein 39 (RNF39), are organized in a tight cluster, and an additional two TRIM genes (namely TRIM38 and TRIM27) telomeric of the cluster within the MHC-I region. The E3 ubiquitin ligases encoded by these genes possess important roles in controlling the intensity of innate immune responses. In this review, we discuss the E3 ubiquitin ligases encoded within the MHC-I region, highlight their regulatory roles in innate immunity, and outline their potential functions in infection, inflammatory and autoimmune diseases.

K27-linked noncanonic ubiquitination in immune regulation

Ubiquitination is a common form of posttranslational modification that has been implicated in regulating considerable immune signaling pathways. The functions of canonic K48- and K63-linked ubiquitination have been well studied. However, the roles of noncanonic ubiquitination remain largely unexplored and require further investigations. There is increasing evidence suggesting that K27-linked noncanonic ubiquitination turns out to be indispensable to both innate immune signaling and T cell signaling. In this review, we provide an overview of the latest findings related to K27-linked ubiquitination, and highlight the crucial roles of K27-linked ubiquitination in regulating antimicrobial response, cytokine signaling and response, as well as T cell activation and differentiation. We also propose interesting areas for better understanding how K27-linked ubiquitination regulates immunity.