Artificial nucleic acid circuits with precisely controllable dynamic and function have shown great promise in biosensing, but their utility in molecular diagnostics is still restrained by the inability to process genomic DNA directly and moderate sensitivity. To address this limitation, we present a CRISPR-Cas–powered catalytic nucleic acid circuit, namely, CRISPR-Cas–only amplification network (CONAN), for isothermally amplified detection of genomic DNA. By integrating the stringent target recognition, helicase activity, and trans-cleavage activity of Cas12a, a Cas12a autocatalysis-driven artificial reaction network is programmed to construct a positive feedback circuit with exponential dynamic in CONAN. Consequently, CONAN achieves one-enzyme, one-step, real-time detection of genomic DNA with attomolar sensitivity. Moreover, CONAN increases the intrinsic single-base specificity of Cas12a, and enables the effective detection of hepatitis B virus infection and human bladder cancer–associated single-nucleotide mutation in clinical samples, highlighting its potential as a powerful tool for disease diagnostics.

Activation of innate immunity is essential for host cells to restrict the spread of invading viruses and other pathogens. However, attenuation or termination of signaling is also necessary for preventing immune-mediated tissue damage and spontaneous autoimmunity. Here, we identify NLRX1 as a negative regulator for MAVS-mediated signaling pathway during HCV infection. Depletion of NLRX1 enhances HCV-triggered activation of IFN signaling and causes the suppression of HCV propagation in hepatocytes. NLRX1, a HCV-inducible protein, interacts with MAVS and mediates the K48-linked polyubiquitination and the subsequent degradation of MAVS via proteasomal pathway. Moreover, PCBP2 interacts with NLRX1 to participate in NLRX1-induced degradation of MAVS and inhibition of antiviral responses during HCV infection. Mutagenic analyses further revealed that the NOD domain of NLRX1 is essential for NLRX1 to interact with PCBP2 and subsequently induce MAVS degradation. Our study unlocks a key mechanism of fine tuning of innate immunity by which NLRX1 restrains RLRs-MAVS signaling cascade by recruiting PCBP2 to MAVS for inducing MAVS degradation through the proteasomal pathway. NLRX1, a negative regulator of innate immunity, is a pivotal host factor for HCV to establish persistent infection. Innate immunity needs to be tightly regulated to maximize antiviral response and minimize immune-mediated pathology. Whereas, the underlying mechanisms are poorly understood. In this study, we report that NLRX1 is a proviral host factor for HCV infection and functions as a negative regulator in HCV-triggered innate immune response. NLRX1 recruits PCBP2 to MAVS and induces the K48-linked polyubiquitination and degradation of MAVS, leading to the negative regulation of IFN signaling pathway and promoting HCV infection. Overall, this study provides intriguing insights into how innate immunity is regulated during viral infection.

Emerging evidence indicates that long noncoding RNAs (lncRNAs) regulate various biological processes, especially innate and adaptive immunity. However, the relationship between lncRNAs and the interferon (IFN) pathway remains largely unknown. Here, we report that lncRNA ITPRIP-1 (lncITPRIP-1) is involved in viral infection and plays a crucial role in the virus-triggered IFN signaling pathway through the targeting of melanoma differentiation-associated gene 5 (MDA5). LncITPRIP-1 can be induced by viral infection, which is not entirely dependent on the IFN signal. Besides, there is no coding potential found in the lncITPRIP-1 transcript. LncITPRIP-1 binds to the C terminus of MDA5, and it possesses the ability to boost the oligomerization of both the full length and the 2 caspase activation and recruitment domains of MDA5 in a K63-linked polyubiquitination-independent manner. Amazingly, we also found that MDA5 can suppress hepatitis C virus (HCV) replication independently of IFN signaling through its C-terminal-deficient domain bound to viral RNA, in which lncITPRIP-1 plays a role as an assistant. In addition, the expression of lncITPRIP-1 is highly consistent with MDA5 expression, indicating that lncITPRIP-1 may function as a cofactor of MDA5. All the data suggest that lncITPRIP-1 enhances the innate immune response to viral infection through the promotion of oligomerization and activation of MDA5. Our study discovers the first lncRNA ITPRIP-1 involved in MDA5 activation. Hepatitis C virus infection is a global health issue, and there is still no available vaccine, which makes it urgent to reveal the underlying mechanisms of HCV and host factors. Although RIG-I has been recognized as the leading cytoplasmic sensor against HCV for a long time, recent findings that MDA5 regulates the IFN response to HCV have emerged. Our work validates the significant role of MDA5 in IFN signaling and HCV infection and proposes the first lncRNA inhibiting HCV replication by promoting the activation of MDA5 and mediating the association between MDA5 and HCV RNA, the study of which may shed light on the MDA5 function and treatment for hepatitis C patients. Our suggested model of how lncITPRIP-1 orchestrates signal transduction for IFN production illustrates the essential role of lncRNAs in virus elimination.

Pancreatic cancer (PC) is a highly malignant tumor with increased morbidity and mortality, which is difficult to diagnose and cure in the clinic. Through secreting exosomes containing biological molecules, including diverse RNAs and proteins, bone marrow mesenchymal stem cells (BM‐MSCs) influence the immunity, inflammation, tumor environment, and cancer metastasis. In this study, low expression of miRNA‐1231 (miR‐1231) in exosomes derived from the peripheral blood was significantly correlated with the TNM stage of PC, suggesting the potential inhibitory effect of exosomal miR‐1231 on PC occurrence and development. The proliferation, migration, invasion, and adhesion to the matrix of PC cells BxPC‐3 and PANC‐1 were negatively regulated by exosomes derived from the supernatants of BM‐MSCs that transfected with miR‐1231 oligonucleotides. Simultaneously, tumor growth in vivo was seriously restrained in BALB/C nude mice by tail vein injection with exosomes originated from BM‐MSCs that transfected with miR‐1231 mimics. The exosomes extracted from BM‐MSCs with high level of miR‐1231 inhibit the activity of PC, providing the potential application for developing new and efficient medicine for cancer therapy, especially for PC treatment. The exosomal miR‐1231 of peripheral blood may also be a potential indicator for PC diagnosis in the future.

Interferons (IFNs) restrict various kinds of viral infection via induction of hundreds of IFN-stimulated genes (ISGs), while the functions of the majority of ISGs are broadly unclear. Here, we show that a high-IFN-inducible gene, ISG12a (also known as IFI27), exhibits a nonapoptotic antiviral effect on hepatitis C virus (HCV) infection. Viral NS5A protein is targeted specifically by ISG12a, which mediates NS5A degradation via a ubiquitination-dependent proteasomal pathway. K374R mutation in NS5A domain III abrogates ISG12a-induced ubiquitination and degradation of NS5A. S-phase kinase-associated protein 2 (SKP2) is identified as an ubiquitin E3 ligase for NS5A. ISG12a functions as a crucial adaptor that promotes SKP2 to interact with and degrade viral protein. Moreover, the antiviral effect of ISG12a is dependent on the E3 ligase activity of SKP2. These findings uncover an intriguing mechanism by which ISG12a restricts viral infection and provide clues for understanding the actions of innate immunity. IMPORTANCE Upon virus invasion, IFNs induce numerous ISGs to control viral spread, while the functions of the majority of ISGs are broadlyunclear. The present study shows a novel antiviral mechanism of ISGs and elucidated that ISG12a recruits an E3 ligase, SKP2, for ubiquitination and degradation of viral protein and restricts viral infection. These findings provide important insights into exploring the working principles of innate immunity.

The ability to harness innate immunity is a promising solution for improving cancer immunotherapy. Interferon (IFN) induces expression of IFN-stimulated genes (ISGs) by activating the JAK-STAT signaling pathway to promote innate immunity and inhibit malignant tumor growth, but the functions and mechanisms of most ISGs in cancer regulation are unknown. As an innate immune effector, ISG12a promotes the innate immune response to viral infection. In this study, ISG12a was found to be expressed at low levels in gastrointestinal cancer, represented by hepatocellular cancer (HCC) and gastric cancer (GC), and it identified as a tumor suppressor that affects clinical prognosis. ISG12a silencing accelerated the malignant transformation and epithelial-mesenchymal transition of cancer cells. Mechanistically, ISG12a promoted β-catenin proteasomal degradation by inhibiting the degradation of ubiquitinated Axin, thereby suppressing the canonical Wnt/β-catenin signaling pathway. Notably, β-catenin was identified as a transcription factor for PD-L1. Inhibition of Wnt/β-catenin signaling by ISG12a suppressed expression of the immune checkpoint PD-L1, rendering cancer cells sensitive to NK cell-mediated killing. This study reveals a mechanism underlying the anticancer effects of IFN. Some ISGs, as represented by ISG12a, may be useful in cancer therapy and prevention. The identified interrelations among innate immunity, Wnt/β-catenin signaling, and cancer immunity may provide new insight into strategies that will improve the efficiency of immunotherapy.

Innate immunity is the essential way for host cells to resist viral infection through the production of IFNs and proinflammatory cytokines. IRF3 plays a critical role in innate immune response to viral infection. However, the role of IRF1 in innate immunity remains largely unknown. In this study, we found that IRF1 is upregulated through IFN/JAK/STAT signaling pathway upon viral infection. Silencing IRF1 attenuates innate immune response to viral infection. IRF1 interacts with IFR3 and augments the activation of IRF3 through blocking the interaction between IRF3 and PP2A. DNA binding domain (DBD) of IRF1 is the key functional domain for its interaction with IRF3. Overall, our study reveals a novel mechanism of by which IRF1 promotes innate immune response to viral infection through enhancing the activation of IRF3, thereby inhibiting viral infection. IMPORTANTCE Activation of innate immunity is essential for host cells to restrict the spread of invading viruses and other pathogens. IRF3 plays a critical role in innate immune response to RNA viral infection. However, whether IRF1 plays a role in innate immunity is unclear. In this study, we demonstrated that IRF1 promotes innate immune response to viral infection. IRF1 is induced by viral infection. Notably, IRF1 targets and augments the phosphorylation of IRF3 through blocking the interaction between IRF3 and PP2A, leading to upregulation of innate immunity. Collectively, our study provides new insight into the regulatory mechanism of IFN signaling and uncovers the role of IRF1 in the positive regulation of innate immune response to viral infection.

The type I interferon (IFN‐I) system is important for antiviral and anticancer immunity. Prolonged activation of IFN/JAK/STAT signaling is closely associated with autoimmune diseases. TRIM10 dysfunction may be associated closely with certain autoimmune disorders. Here, we observed that the serum TRIM10 protein level is lower in patients with systemic lupus erythematosus than in healthy control subjects. We speculated the possible involvement of TRIM10‐induced modulation of the IFN/JAK/STAT signaling pathway in systemic lupus erythematosus. In line with our hypothesis, TRIM10 inhibited the activation of JAK/STAT signaling pathway triggered by various stimuli. TRIM10 restricted the IFN‐I/JAK/STAT signaling pathway, which was independent of its E3 ligase activity. Mechanistically, TRIM10 interacted with the intracellular domain of IFNAR1 and blocked the association of IFNAR1 with TYK2. These data suggest the possible TRIM10 suppresses IFN/JAK/STAT signaling pathway through blocking the interaction between IFNAR1 and TYK2. Targeting TRIM10 is a potential strategy for treating autoimmune diseases.