MAVS promotes interferon signaling in RNA virus infection by ZUFSP-mediated chromatin regulation.

Mitochondria serve as a platform for innate immune signaling transduction, and mitochondrial antiviral signaling protein (MAVS) is essential for interferon-ß (IFN-ß) production and innate antiviral immunity against RNA viruses. Here, we identified zinc finger-containing ubiquitin peptidase 1 (ZUFSP/ZUP1) as a MAVS-interacting protein by using proximity-based labeling technology in HEK293T and found it could act as a positive regulator of the retinoic acid-inducible gene-I (RIG-I)-like receptors(RLRs), including RIG-I and interferon-induced helicase C domain-containing protein 1 (MDA5). ZUFSP deficiency markedly inhibited RNA virus-triggered induction of downstream antiviral genes, and Zufsp-deficient mice were more susceptible to RNA virus infection. After RNA virus infection,ZUFSP was translocated from cytoplasm to nucleus and interacted with chromatin remodeling complex to facilitate the opening of IFN-stimulated gene (ISG) loci for transcription. This study provides a critical mechanistic basis for MAVS-regulated chromatin remodeling to promote interferon signaling.

Nicotinamide N-Methyl Transferase as a Predictive Marker of Tubular Fibrosis in CKD.

Purpose: Chronic kidney disease (CKD) progression is complex. There are not standardized methods for predicting the prognosis of CKD. Nicotinamide N-methyltransferase (NNMT) has been shown to be associated with renal fibrosis. This study aimed to validate NNMT as a prognostic biomarker of progressive CKD. Patients and Methods: We explored the relationship between NNMT expression and CKD-related outcome variables using the NephroseqV5 and GEO databases. Additionally, a validation set of 37 CKD patients was enrolled to measure the correlation between NNMT expression levels and CKD outcomes. Furthermore, single-cell RNA sequencing data and the Human Protein Atlas were reanalyzed to investigate the expression specificity of NNMT in the kidney. Finally, to detect the status of NNMT expression with tubular fibrosis in vivo, we constructed a unilateral ureteral obstruction (UUO) mouse treated with an NNMT inhibitor. Results: Analyzing the datasets showed that NNMT was expressed mainly in proximal tubule compartments. And patients with high NNMT expression levels had a significantly lower overall survival rate compared to those with low NNMT expression levels (P = 0.013). NNMT was independent of prognosis factors in the multivariate Cox regression model, and the AUCs for CKD progression at 1, 3, and 5 years were 0.849, 0.775, and 0.877, respectively. Pathway enrichment analysis indicated that NNMT regulates the biological processes of tubulointerstitial fibrosis (TIF). In the validation group, NNMT levels were significantly higher in the CKD group combined with interstitial fibrosis. In vivo, NNMT was a high expression in the UUO group, peaking at postoperative day 21. Treatment with an NNMT inhibitor improved renal tubular interstitial fibrosis, and expression levels of FN, α-SMA, VIM, and TGF-ß1 were decreased compared with UUO (P < 0.05). Conclusion: NNMT was expressed mainly in tubular renal compartments, and associated with CKD prognosis. It holds potential as a diagnostic biomarker for tubular fibrosis in CKD.

XAF1 promotes anti-RNA virus immune responses by regulating chromatin accessibility.

A rapid induction of antiviral genes is critical for eliminating viruses, which requires activated transcription factors and opened chromatins to initiate transcription. However, it remains elusive how the accessibility of specific chromatin is regulated during infection. Here, we found that XAF1 functioned as an epigenetic regulator that liberated repressed chromatin after infection. Upon RNA virus infection, MAVS recruited XAF1 and TBK1. TBK1 phosphorylated XAF1 at serine-252 and promoted its nuclear translocation. XAF1 then interacted with TRIM28 with the guidance of IRF1 to the specific locus of antiviral genes. XAF1 de-SUMOylated TRIM28 through its PHD domain, which led to increased accessibility of the chromatin and robust induction of antiviral genes. XAF1-deficient mice were susceptible to RNA virus due to impaired induction of antiviral genes. Together, XAF1 acts as an epigenetic regulator that promotes the opening of chromatin and activation of antiviral immunity by targeting TRIM28 during infection.

SAFA facilitates chromatin opening of immune genes through interacting with anti-viral host RNAs.

Regulation of chromatin structure and accessibility determines the transcription activities of genes, which endows the host with function-specific patterns of gene expression. Upon viral infection, the innate immune responses provide the first line of defense, allowing rapid production of variegated antiviral cytokines. Knowledge on how chromatin accessibility is regulated during host defense against viral infection remains limited. Our previous work found that the nuclear matrix protein SAFA surveilled viral RNA and regulated antiviral immune genes expression. However, how SAFA regulates the specific induction of antiviral immune genes remains unknown. Here, through integration of RNA-seq, ATAC-seq and ChIP-seq assays, we found that the depletion of SAFA specifically decreased the chromatin accessibility, activation and expression of virus induced genes. And mutation assays suggested that the RNA-binding ability of SAFA was essential for its function in regulating antiviral chromatin accessibility. RIP-seq results showed that SAFA exclusively bound with antiviral related RNAs following viral infection. Further, we combined the CRISPR-Cas13d mediated RNA knockdown system with ATAC-qPCR, and demonstrated that the binding between SAFA and according antiviral RNAs specifically mediated the openness of the corresponding chromatin and following robust transcription of antiviral genes. Moreover, knockdown of these associated RNAs dampened the accessibility of related genes in an extranuclear signaling pathway dependent manner. Interestingly, VSV infection cleaved SAFA protein at the C-terminus which deprived its RNA binding ability for immune evasion. Thus, our results demonstrated that SAFA and the interacting RNA products collaborated and remodeled chromatin accessibility to facilitate antiviral innate immune responses.

Suppression of ELF4 in ulcerative colitis predisposes host to colorectal cancer.

Ulcerative colitis (UC) is a chronic inflammatory bowel disease, characterized by relapsing and remitting colon mucosal inflammation. For patients suffering from UC, a higher risk of colon cancer has been widely recognized. Here, we found that Elf4 -/- mice developed colon tumors with 3 cycles of dextran sulfate sodium salt (DSS) treatment alone. We further showed that ELF4 suppression was prevalent in both patients with UC and DSS-induced mice models, and this suppression was caused by promoter region methylation. ELF4, upon PARylation by PARP1, transcriptionally regulated multiple DNA damage repair machinery components. Consistently, ELF4 deficiency leads to more severe DNA damage both in vitro and in vivo. Oral administration of montmorillonite powder can prevent the reduction of ELF4 in DSS-induced colitis models and lower the risk of colon tumor development during azoxymethane (AOM) and DSS induced colitis-associated cancer (CAC). These data provided additional mechanism of CAC initiation and supported the "epigenetic priming model of tumor initiation".

CBRPP: a new RNA-centric method to study RNA-protein interactions.

RNA and protein are interconnected biomolecules that can influence each other's life cycles and functions through physical interactions. Abnormal RNA-protein interactions lead to cell dysfunctions and human diseases. Therefore, mapping networks of RNA-protein interactions is crucial for understanding cellular processes and pathogenesis of related diseases. Different practical protein-centric methods for studying RNA-protein interactions have been reported, but few robust RNA-centric methods exist. Here, we developed CRISPR-based RNA proximity proteomics (CBRPP), a new RNA-centric method to identify proteins associated with an endogenous RNA of interest in native cellular context without pre-editing of the target RNA, cross-linking or RNA-protein complexes manipulation in vitro. CBRPP is based on a fusion of dCas13 and proximity-based labelling (PBL) enzyme. dCas13 can deliver PBL enzyme to the target RNA with high specificity, while PBL enzyme labels the surrounding proteins of the target RNA, which are then identified by mass spectrometry.

The mitochondrial protein ERAL1 suppresses RNA virus infection by facilitating RIG-I-like receptor signaling.

Mitochondria not only serve as a platform for innate immune signaling transduction but also enhance immune responses by releasing mitochondrial DNA and RNA into the cytoplasm. However, whether mitochondrial matrix proteins could be liberated and involved in immune responses remains enigmatic. Here, we identify the mitochondrial protein ERA G-protein-like 1 (ERAL1) as a mitochondrial antiviral signaling protein (MAVS)-interacting protein by using proximity-based labeling technology. ERAL1 deficiency markedly reduces the downstream antiviral signaling triggered by RNA viruses. Moreover, ERAL1-deficient mice are more susceptible to lethality following RNA virus infection than wild-type mice. After virus infection, ERAL1 is released from mitochondria through the BAX/BAK pore. The cytosolic ERAL1 facilitates lysine 63 (K63)-linked ubiquitination of retinoicacid inducible gene-1 (RIG-I)/melanoma differentiation-associated gene 5 (MDA5) and promotes downstream MAVS polymerization, thus positively regulating antiviral responses.

Cytosolic and nuclear recognition of virus and viral evasion.

The innate immune system is the first line of host defense, which responds rapidly to viral infection. Innate recognition of viruses is mediated by a set of pattern recognition receptors (PRRs) that sense viral genomic nucleic acids and/or replication intermediates. PRRs are mainly localized either to the endosomes, the plasma membrane or the cytoplasm. Recent evidence suggested that several proteins located in the nucleus could also act as viral sensors. In turn, these important elements are becoming the target for most viruses to evade host immune surveillance. In this review, we focus on the recent progress in the study of viral recognition and evasion.

The Nuclear Matrix Protein SAFA Surveils Viral RNA and Facilitates Immunity by Activating Antiviral Enhancers and Super-enhancers.

Pathogen pattern recognition receptors (PRRs) trigger innate immune responses to invading pathogens. All known PRRs for viral RNA have extranuclear localization. However, for many viruses, replication generates dsRNA in the nucleus. Here, we show that the nuclear matrix protein SAFA (also known as HnRNPU) functions as a nuclear viral dsRNA sensor for both DNA and RNA viruses. Upon recognition of viral dsRNA, SAFA oligomerizes and activates the enhancers of antiviral genes, including IFNB1. Moreover, SAFA is required for the activation of super-enhancers, which direct vigorous immune gene transcription to establish the antiviral state. Myeloid-specific SAFA-deficient mice were more susceptible to lethal HSV-1 and VSV infection, with decreased type I IFNs. Thus, SAFA functions as a nuclear viral RNA sensor and trans-activator to bridge innate sensing with chromatin remodeling and potentiate robust antiviral responses.

The GRA15 protein from Toxoplasma gondii enhances host defense responses by activating the interferon stimulator STING.

Toxoplasma gondii is an important neurotropic pathogen that establishes latent infections in humans that can cause toxoplasmosis in immunocompromised individuals. It replicates inside host cells and has developed several strategies to manipulate host immune responses. However, the cytoplasmic pathogen-sensing pathway that detects T. gondii is not well-characterized. Here, we found that cyclic GMP-AMP synthase (cGAS), a sensor of foreign dsDNA, is required for activation of anti-T. gondii immune signaling in a mouse model. We also found that mice deficient in STING (Stinggt/gt mice) are much more susceptible to T. gondii infection than WT mice. Of note, the induction of inflammatory cytokines, type I IFNs, and interferon-stimulated genes in the spleen from Stinggt/gt mice was significantly impaired. Stinggt/gt mice exhibited more severe symptoms than cGAS-deficient mice after T. gondii infection. Interestingly, we found that the dense granule protein GRA15 from T. gondii is secreted into the host cell cytoplasm and then localizes to the endoplasmic reticulum, mediated by the second transmembrane motif in GRA15, which is essential for activating STING and innate immune responses. Mechanistically, GRA15 promoted STING polyubiquitination at Lys-337 and STING oligomerization in a TRAF protein-dependent manner. Accordingly, GRA15-deficient T. gondii failed to elicit robust innate immune responses compared with WT T. gondii. Consequently, GRA15-/-T. gondii was more virulent and caused higher mortality of WT mice but not Stinggt/gt mice upon infection. Together, T. gondii infection triggers cGAS/STING signaling, which is enhanced by GRA15 in a STING- and TRAF-dependent manner.

Proportion of neuropathic pain in the back region in chronic low back pain patients -a multicenter investigation.

Neuropathy can contribute to low back pain (LBP) in the region of the back. Our study investigated the proportion of neuropathic pain (NP) in low back region in chronic LBP patients from multicenter and clinics in China and identified associated factors. Assessment was made using a questionnaire and the Leeds Assessment of Neuropathic Symptoms and Signs (LANSS, only tested in low back region), as well as Quantitative Sensory Testing (QST, merely applied to the low back region), the Hospital Anxiety and Depression Scale (HADS) and the Oswestry Disability Index (ODI). Our questionnaire collected demographic information, behavioral habits and medical records. 2116 outpatients over 18 years old complaining of LBP lasting more than 3 months were enrolled in this study. The NP proportion in low back region in chronic LBP patients was 2.8%. Multivariable logistic regression analysis showed that histories of lumbar surgery, abdominal or pelvic surgery, and drinking alcohol were independent positive predictors for LBP of predominantly neuropathic origin (LBNPO), while history of low back sprain and frequently carrying weight as independent negative predictor. Using these parameters may help the identification of patients with chronic LBP likely to develop NP leading to improved treatment outcomes.