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

Highlights d METTL5 shows strong substrate preference to 18S rRNA m 6 A1832 motif UAACA d The m 6 A1832 modification may affect decoding center in favoring mRNA binding d METTL5 promotes translation initiation, S6K activation, and breast cancer cell growth d C. elegans METL-5 regulates stress response, lifespan, and UPR ER

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Embryonic stem cells (ESCs) are pluripotent stem cells with the ability to self‐renew and to differentiate into any cell types of the 3 germ layers. Recent studies have demonstrated that there is a strong connection between mitochondrial function and pluripotency. Here, we report that methyltransferase like (Mettl) 17, identified from the clustered regularly interspaced short palindromic repeats knockout screen, is required for proper differentiation of mouse embryonic stem cells (mESCs). Mettl17 is located in mitochondria through its N‐terminal targeting sequence and specifically interacts with 12S mitochondrial ribosomal RNA (mt‐rRNA) as well as small subunits of mitochondrial ribosome (MSSUs). Loss of Mettl17 affects the stability of both 12S mt‐rRNA and its associated proteins of MSSUs. We further showed that Mettl17 is an S‐adenosyl methionine (SAM)‐binding protein and regulates mitochondrial ribosome function in a SAM‐binding–dependent manner. Loss of Mettl17 leads to around 70% reduction of m4C840 and 50% reduction of m5C842 of 12S mt‐rRNA, revealing the first regulator of the m4C840 and indicating a crosstalk between the 2 nearby modifications. The defects of mitochondrial ribosome caused by deletion of Mettl17 lead to the impaired translation of mitochondrial protein‐coding genes, resulting in significant changes in mitochondrial oxidative phosphorylation and cellular metabolome, which are important for mESC pluripotency.—Shi, Z., Xu, S., Xing, S., Yao, K., Zhang, L., Xue, L., Zhou, P., Wang, M., Yan, G., Yang, P., Liu, J., Hu, Z., Lan, F. Mettl17 a regulator of mitochondrial ribosomal RNA modifications is required for the translation of mitochondrial coding genes. FASEB J. 33, 13040–13050 (2019). http://www.fasebj.org

Agrobacterium tumefaciens infects and causes crown galls in dicot plants by transferring T-DNA from the Ti plasmid to the host plant via a type IV secretion system. This process requires appropriate environmental conditions, certain plant secretions, and bacterial regulators. In our previous work, a member of the LysR family of transcriptional regulators (LsrB) in Sinorhizobium meliloti was found to modulate its symbiotic interactions with the host plant alfalfa. However, the function of its homolog in A. tumefaciens remains unclear. In this study, we show that the LsrB protein of A. tumefaciens is required for efficient transformation of host plants. A lsrB deletion mutant of A. tumefaciens exhibits a number of defects, including in succinoglycan production, attachment, and resistance to oxidative stress and iron limitation. RNA-sequencing analysis indicated that 465 genes were significantly differentially expressed (upregulation of 162 genes and downregulation of 303 genes) in the mutant, compared with the wild-type strain, including those involved in succinoglycan production, iron transporter, and detoxification enzymes for oxidative stress. Moreover, expression of the lsrB gene from S. meliloti, Brucella abortus, or A. tumefaciens rescued the defects observed in the S. meliloti or A. tumefaciens lsrB deletion mutant. Our findings suggest that a conserved mechanism of LsrB function exists in symbiotic and pathogenic bacteria of the family Rhizobiaceae.

The development of legume nitrogen-fixing nodules is regulated by reactive oxygen species (ROS) produced by symbionts. Several regulators from Rhizobium are involved in ROS sensing. In a previous study, we found that Sinorhizobium meliloti LsrB regulates lipopolysaccharide production and is associated with H O accumulation in alfalfa (Medicago sativa) nodules. However, its underlying regulatory mechanism remains unclear. Here, we report that the cysteine residues in LsrB are required for adaptation to oxidative stress, gene expression, alfalfa nodulation and nitrogen fixation. Moreover, LsrB directly activated the transcription of lrp3 and gshA (encoding γ-glutamylcysteine synthetase, responsible for glutathione synthesis) and this regulation required the cysteine (Cys) residues in the LsrB substrate-binding domain. The Cys residues could sense oxidative stress via the formation of intermolecular disulfide bonds, generating LsrB dimers and LsrB-DNA complexes. Among the Cys residues, C238 is a positive regulatory site for the induction of downstream genes, whereas C146 and C275 play negative roles in the process. The lsrB mutants with Cys-to-Ser substitutions displayed altered phenotypes in respect to their adaptation to oxidative stress, nodulation and nitrogen fixation-related plant growth. Our findings demonstrate that S. meliloti LsrB modulates alfalfa nodule development by directly regulating downstream gene expression via a post-translational strategy.

The coronavirus induced disease 19 caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a worldwide threat to human lives, and neutralization antibodies present a great therapeutic potential in curing affected patients. We purified more than one thousand memory B cells specific to SARS-CoV-2 recombinant S1 or RBD antigens from 11 convalescent COVID-19 patients, and a total of 729 naturally paired heavy and light chain fragments were obtained by single B cell cloning technology. Among these, 178 recombinant monoclonal antibodies were tested positive for antigen binding, and 17 strong binders to S1 or RBD were identified with Kd(EC50) below 1 nM. Importantly, 12 antibodies could block pseudoviral entry into HEK293T cells overexpressing ACE2, with the best ones showing IC50 around 2-3 nM. From these 12 antibodies, we had tested two in authentic virus infection assay, and found one was able to effectively block live viral entry with IC50 around or below 15 nM. Interestingly, we also found a substantial portion of these antibodies crossreacting with the SARS-CoV spike protein.Altogether, our study provided potent neutralization antibodies as clinical therapeutics candidates for further development.

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