N-methyladenosine (mA) is an abundant modification in eukaryotic mRNA, regulating mRNA dynamics by influencing mRNA stability, splicing, export, and translation. However, the precise mA regulating machinery still remains incompletely understood. Here we demonstrate that ZC3H13, a zinc-finger protein, plays an important role in modulating RNA mA methylation in the nucleus. We show that knockdown of Zc3h13 in mouse embryonic stem cell significantly decreases global mA level on mRNA. Upon Zc3h13 knockdown, a great majority of WTAP, Virilizer, and Hakai translocate to the cytoplasm, suggesting that Zc3h13 is required for nuclear localization of the Zc3h13-WTAP-Virilizer-Hakai complex, which is important for RNA mA methylation. Finally, Zc3h13 depletion, as does WTAP, Virilizer, or Hakai, impairs self-renewal and triggers mESC differentiation. Taken together, our findings demonstrate that Zc3h13 plays a critical role in anchoring WTAP, Virilizer, and Hakai in the nucleus to facilitate mA methylation and to regulate mESC self-renewal.

Summary Regulation of enhancer activity is important for controlling gene expression programs. Here we report that a biochemical complex that contains a potential chromatin reader, RACK7 and the histone lysine 4 tri-methyl (H3K4me3)-specific demethylase KDM5C occupies many active enhancers, including almost all super-enhancers. Loss of RACK7 or KDM5C results in overactivation of enhancers, characterized by the deposition of H3K4me3 and H3K27Ac, together with increased transcription of eRNAs and nearby genes. Furthermore, loss of RACK7 or KDM5C leads to de-repression of S100A oncogenes and various cancer-related phenotypes. Our findings reveal a RACK7/KDM5C-regulated, dynamic interchange between histone H3K4me1 and H3K4me3 at active enhancers, representing an additional layer of regulation of enhancer activity. We propose that RACK7/KDM5C functions as an enhancer “brake” to ensure appropriate enhancer activity, which, when compromised, could contribute to tumorigenesis.

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Highlights d 11 neutralizing antibodies against SARS-CoV-2 target three main epitopes on RBD d Epitope-A antibody 414-1 shows neutralizing IC 50 at 1.75 nM d Epitope-B antibody 553-15 can enhance the neutralizing abilities of other antibodies d One neutralizing antibody, 515-5, can cross neutralize SARS-CoV pseudovirus

The innate immune system initiates immune responses by pattern-recognition receptors (PRR). Virus-derived nucleic acids are sensed by the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) family and the toll-like receptor (TLR) family as well as the DNA sensor cyclic GMP-AMP (cGAMP) synthase (cGAS). These receptors activate IRF3/7 and NF-κB signaling pathways to induce the expression of type I interferons (IFNs) and other cytokines firing antiviral responses within the cell. However, to achieve a favorable outcome for the host, a balanced production of IFNs and activation of antiviral responses is required. Posttranslational modifications (PTMs), such as the covalent linkage of functional groups to amino acid chains, are crucial for this immune homeostasis in antiviral responses. Canonical PTMs including phosphorylation and ubiquitination have been extensively studied and other PTMs such as methylation, acetylation, SUMOylation, ADP-ribosylation and glutamylation are being increasingly implicated in antiviral innate immunity. Here we summarize our recent understanding of the most important PTMs regulating the antiviral innate immune response, and their role in virus-related immune pathogenesis.Keywords: Antiviral immunity r Interferons r Phosphorylation r Post-translational modifications r PRR r Ubiquitination IntroductionInfectious diseases, especially virus infections, are still a serious threat to humanity and the host innate immune system represents a critical defense against invading viruses. Host cells can initiate these innate immune responses by detecting viral DNA and RNA with a set of pattern recognition receptors (PRRs) including the toll-like receptor (TLR) family and the retinoic acid-inducible gene I (RIG-I)-like receptor (RLR) family, as well as cytosolic DNA sensors such as cyclic GMP-AMP (cGAMP) synthase (cGAS), IFI16 and DDX41 [1,2]. After recognition of viral nucleic acids, these PRRs trigger the production of proinflammatory cytokines, chemokines and type I interferons (IFNs), which subsequently induce synthesis of antiviral proteins, death of infected cells and activation of the adaptive immune response [3,4]. These antiviral signals Correspondence: Dr. Baoxue Ge e-mail: gebaoxue@sibs.ac.cn must be spatially and temporally orchestrated to achieve an optimal outcome for the host and much attention has been raised to understanding the signaling pathways and regulatory factors in the antiviral innate immunity.Toll-like receptors, including TLR3, TLR7, TLR8 and TLR9, sense endosomal nucleic acids derived from the enclosed microbes and infected apoptotic cells. While TLR9 detects unmethylated CpG DNA species, TLR3 and TLR7/8 recognize double-stranded RNA (dsRNA) and single-stranded RNA (ssRNA), respectively [5] ( Fig. 1). Following ligand binding, the TLRs form a signaling platform in which distinct Toll/interleukin-1 receptor (TIR) domaincontaining adaptors are engaged. For instance, TLR3 signals via TIR-domain-containing adaptor protein inducing interferon beta (TRIF), and TLR7/8/9 rel...

The immune-response gene 1 (IRG1) plays a key role in anti-pathogen defense, as deletion of Irg1 in mice causes severe defects in response to bacterial and viral infection, and decreased survival 1, 2 . IRG1 transcription is rapidly induced by pathogen infection and in ammatory conditions primarily in cells of myeloid lineage 3 . IRG1 encodes a mitochondrial metabolic enzyme, aconitate decarboxylase 1 (ACOD1), that catalyzes the decarboxylation of cis-aconitate to produce the anti-in ammatory metabolite itaconic acid (ITA) 4 . Several molecular processes are affected by ITA, including succinate dehydrogenase (SDH) inhibition 5 , resulting in succinate accumulation and metabolic reprogramming 6,7 , and alkylation of protein cysteine residues, inducing the electrophilic stress response mediated by NRF2 and IκBζ 8, 9 and impairing aerobic glycolysis 10 . However, the mechanisms by which ITA exerts its profound antiin ammatory effect still remains to be fully elucidated. Here, we show that ITA is a potent inhibitor of the TET family DNA dioxygenases, which catalyze the conversion of 5-methylcytosine (5mC) to 5hydroxymethylcytosine (5hmC) during the process of active DNA demethylation. ITA binds to the same site of α-ketoglutarate (α-KG) in TET2, inhibiting its catalytic activity. Lipopolysaccharides (LPS) treatment, which induces Irg1 expression and ITA accumulation, inhibits Tet activity in macrophages. Transcriptome analysis reveals TET2 is a major target of ITA in suppressing LPS-induced genes, including those regulated by NF-κB and STAT signaling pathways. In vivo, ITA decreases 5hmC, reduces LPS-induced acute pulmonary edema and lung and liver injury, and protects mice against lethal endotoxaemia in a manner that is dependent on the catalytic activity of Tet2. Our study thus identi es ITA as an immune modulatory metabolite that selectively inhibits TET enzymes to dampen the in ammatory response. MainDeletion of the Irg1 gene or treatment with cell permeable ITA alters the transcriptional signature in response to LPS 2 . We speculated that ITA may impact epigenetics to in uence gene expression, and therefore, we determined the effect of Irg1 expression and ITA accumulation on global histone and DNA de/methylation in transfected HEK293T cells (Extended Data Fig. 1a). We found that ectopic expression of either wild-type or catalytic inactive mutant Irg1 had little effect on mono-, di-, and trimethylation of all ve histone H3 lysine residues (Extended Data Fig. 1b, 1c). In contrast, expression of wild-type Irg1, but not the catalytic inactive mutant, dramatically reduced Tet2-mediated global 5hmC in cells (Fig. 1a and Extended Data Fig. 1d-e). Like α-KG, which is a crucial co-substrate for the activity of TET2, ITA is also a dicarboxylic acid containing a 4-or 5-carboxylate that, in the case of α-KG, forms hydrogen and ionic bonds with H1416, R1896, and S1898 in TET2 11 . Of note, α-KG binds to Fe(II) in a bidentate manner via its C-1 carboxylate and C-2 keto groups, which are lacking in ITA. This raises the possibi...

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