Pan-cancer analysis of the tumorigenic role of Fanconi anemia complementation group D2 (FANCD2) in human tumors.

Monoubiquitination of FANCD2 is a central step in the activation of the Fanconi anemia (FA) pathway after DNA damage. Defects in the FA pathway centered around FANCD2 not only lead to genomic instability but also induce tumorigenesis. At present, few studies have investigated FANCD2 in tumors, and no pan-cancer research on FANCD2 has been conducted. We conducted a comprehensive analysis of the role of FANCD2 in cancer using public databases and other published studies. Moreover, we evaluated the role of FANCD2 in the proliferation, migration and invasion of lung adenocarcinoma cells through in vitro and in vivo experiments, and explored the role of FANCD2 in cisplatin chemoresistance. We investigated the regulatory effect of FANCD2 on the cell cycle of lung adenocarcinoma cells by flow cytometry, and verified this effect by western blotting. FANCD2 expression is elevated in most TCGA tumors and shows a strong positive correlation with poor prognosis in tumor patients. In addition, FANCD2 expression shows strong correlations with immune infiltration, immune checkpoints, the tumor mutation burden (TMB), and microsatellite instability (MSI), which are immune-related features, suggesting that it may be a potential target of tumor immunotherapy. We further found that FANCD2 significantly promotes the proliferation, invasion, and migration abilities of lung adenocarcinoma cells and that its ability to promote cancer cell proliferation may be achieved by modulating the cell cycle. The findings indicate that FANCD2 is a potential biomarker and therapeutic target in cancer treatment by analyzing the oncogenic role of FANCD2 in different tumors.

LTN1 promotes RLR degradation to inhibit immune response to RNA virus through the ESCRT pathway.

The excessive activation of immune responses will trigger autoimmune diseases or inflammatory injury. The endosomal sorting complexes required for transport (ESCRT) system can capture and mediate ubiquitinated protein degradation, which timely terminates signaling pathway hyperactivation. However, whether the ESCRT system participates in regulating RIGI-like receptor (RLR)-mediated antiviral responses remains unknown. In this study, we show that LTN1/listerin, a major component of RQC, can recruit E3 ubiquitin ligase TRIM27 to trigger K63-linked polyubiquitination of RIGI and IFIH1/MDA5. This K63-linked polyubiquitination facilitates the sorting and degradation of RIGI and IFIH1 proteins through the ESCRT-dependent pathway. Concordantly, LTN1 deficiency enhances the innate antiviral response to infection with RNA viruses. Thus, our work uncovers a new mechanism for RIGI and IFIH1 degradation and identifies the role of LTN1 in negatively regulating RLR-mediated antiviral innate immunity, which may provide new targets for the intervention of viral infection.Abbreviation: 5'-pppRNA: 5' triphosphate double stranded RNA; ATG5: autophagy related 5; ATG7: autophagy related 7; BafA1: bafilomycin A1; ESCRT: endosomal sorting complexes required for transport; CHX: cycloheximide; IFIH1/MDA5: interferon induced with helicase C domain 1; IFN: interferon; PIK3C3/VPS34: phosphatidylinositol 3-kinase catalytic subunit type 3; RIGI: RNA sensor RIG-I; RLR: RIGI-like receptors; RQC: ribosome-associated protein quality control; SeV: Sendai virus; TRIM27: tripartite motif-containing 27; VSV: vesicular stomatitis virus; VPS4: vacuolar protein sorting 4.

Listerin promotes cGAS protein degradation through the ESCRT pathway to negatively regulate cGAS-mediated immune response.

The enzyme cyclic GMP-AMP synthase (cGAS) is a key sensor for detecting misplaced double-stranded DNA (dsDNA) of genomic, mitochondrial, and microbial origin. It synthesizes 2'3'-cGAMP, which in turn activates the stimulator of interferon genes pathway, leading to the initiation of innate immune responses. Here, we identified Listerin as a negative regulator of cGAS-mediated innate immune response. We found that Listerin interacts with cGAS on endosomes and promotes its K63-linked ubiquitination through recruitment of the E3 ligase TRIM27. The polyubiquitinated cGAS is then recognized by the endosomal sorting complexes required for transport machinery and sorted into endosomes for degradation. Listerin deficiency enhances the innate antiviral response to herpes simplex virus 1 infection. Genetic deletion of Listerin also deteriorates the neuroinflammation and the ALS disease progress in an ALS mice model; overexpression of Listerin can robustly ameliorate disease progression in ALS mice. Thus, our work uncovers a mechanism for cGAS regulation and suggests that Listerin may be a promising therapeutic target for ALS disease.

USP5 attenuates NLRP3 inflammasome activation by promoting autophagic degradation of NLRP3.

ABBREVIATIONS: 3-MA: 3-methyladenine; AIM2: absent in melanoma 2; ATG5: autophagy related 5; BafA1: bafilomycin A1; CASP1: caspase 1; CHX: cycloheximide; Co-IP: co-immunoprecipitation; CQ: chloroquine; DUBs: deubiquitinases; IL1B/IL-1ß: interleukin 1 beta; LAMP1: lysosomal associated membrane protein 1; LPS: lipopolysaccharide; MARCHF7/MARCH7: membrane associated RING-CH-type finger 7; NFKB/NF-κB: nuclear factor kappa B; Nig.: nigericin; NLRC4: NLR family CARD domain containing 4; NLRP3: NLR family pyrin domain containing 3; PECs: peritoneal exudate cells; PMN: polymorphonuclear; PMs: peritoneal macrophages; PYCARD/ASC: PYD and CARD domain containing; TLRs: toll like receptors; TNF/TNF-α: tumor necrosis factor; Ub: ubiquitin; USP5: ubiquitin specific peptidase 5; WT: wild type.

Methyltransferase-Like Protein 14 Attenuates Mitochondrial Antiviral Signaling Protein Expression to Negatively Regulate Antiviral Immunity via N6 -methyladenosine Modification.

Mitochondrial antiviral signaling (MAVS) protein is the core signaling adaptor in the RNA signaling pathway. Thus, appropriate regulation of MAVS expression is essential for antiviral immunity against RNA virus infection. However, the regulation of MAVS expression at the mRNA level especially at the post transcriptional level is not well-defined. Here, it is reported that the MAVS mRNA undergoes N6 -methyladenosine (m6 A) modification through methyltransferase-like protein 14 (METTL14), which leads to a fast turnover of MAVS mRNA. Knockdown or deficiency of METTL14 increases MAVS mRNA stability, and downstream phosphorylation of TBK1/IRF3 and interferon-ß production in response to RNA viruses. Compared to wild-type mice, heterozygotes Mettl14+/- mice better tolerate RNA virus infection. The authors' findings unveil a novel mechanism to regulate the stability of MAVS transcripts post-transcriptionally through m6 A modification.

TRIM26 positively regulates the inflammatory immune response through K11-linked ubiquitination of TAB1.

Protein ubiquitination plays an important role in the regulation of TGF-ß-activated kinase 1 (TAK1)-mediated NF-κB activation. It is well established that TAK1 activation is tightly regulated with its binding partners, TAK1-binding proteins (TAB1-3). However, the tight regulation of TAK1 activation remains elusive. Here, using Trim26-knockout mice and Trim26-transgenic mice, we found that TRIM26 acts as a positive regulator of TAK1 activation by ubiquitinating its binding partner TAB1. Knockout of Trim26 inhibited TAK1 activation and downstream kinases activation, thus decreasing the induction of proinflammatory cytokines following LPS, TNF-α, and IL-1ß stimulation. Mechanistically, TRIM26 catalyzes the K11-linked polyubiquitination of TAB1 at Lys294, Lys319, and Lys335 to enhance the activation of TAK1 and subsequent NF-κB and MAPK signaling. Consequently, Trim26 deficiency protects mice from LPS-induced septic shock in vivo. Moreover, Trim26 deficiency attenuates the severity of dextran sodium sulfate (DSS)-induced colitis. Thus, these finding provides a novel insight into how TAK1 activation is regulated through TRIM26-mediated ubiquitination of TAB1 and reveals the new function of TRIM26 in the regulation of the inflammatory innate immune response.

OTUD5 promotes innate antiviral and antitumor immunity through deubiquitinating and stabilizing STING.

Stimulator of interferon genes (STING) is an adaptor protein that is critical for effective innate antiviral and antitumor immunity. The activity of STING is heavily regulated by protein ubiquitination, which is fine-tuned by both E3 ubiquitin ligases and deubiquitinases. Here, we report that the deubiquitinase OTUD5 interacts with STING, cleaves its K48-linked polyubiquitin chains, and promotes its stability. Consistently, knockout of OTUD5 resulted in faster turnover of STING and subsequently impaired type I IFN signaling following cytosolic DNA stimulation. More importantly, Lyz2-Cre Otud5fl/Y mice and CD11-Cre Otud5fl/Y mice showed more susceptibility to herpes simplex virus type 1 (HSV-1) infection and faster development of melanomas than their corresponding control littermates, indicating that OTUD5 is indispensable for STING-mediated antiviral and antitumor immunity. Our data suggest that OTUD5 is a novel checkpoint in the cGAS-STING cytosolic DNA sensing pathway.