Here we describe the complete genome of a new ebolavirus, Bombali virus (BOMV) detected in free-tailed bats in Sierra Leone (little free-tailed (Chaerephon pumilus) and Angolan free-tailed (Mops condylurus)). The bats were found roosting inside houses, indicating the potential for human transmission. We show that the viral glycoprotein can mediate entry into human cells. However, further studies are required to investigate whether exposure has actually occurred or if BOMV is pathogenic in humans.

Highlights d Highly infectious recombinant VSV expressing SARS-CoV-2 spike (S) was generated d rVSV-SARS-CoV-2 S resembles SARS-CoV-2 in entry and inhibitor or antibody sensitivity d rVSV-SARS-CoV-2 S affords rapid screens and forwardgenetic analyses of antivirals Authors

Formation of the 30S initiation complex (30S IC) is an important checkpoint in regulation of gene expression. The selection of mRNA, correct start codon, and the initiator fMet-tRNAfMet requires the presence of three initiation factors (IF1, IF2, IF3) of which IF3 and IF1 control the fidelity of the process, while IF2 recruits fMet-tRNAfMet. Here we present a cryo-EM reconstruction of the complete 30S IC, containing mRNA, fMet-tRNAfMet, IF1, IF2, and IF3. In the 30S IC, IF2 contacts IF1, the 30S subunit shoulder, and the CCA end of fMet-tRNAfMet, which occupies a novel P/I position (P/I1). The N-terminal domain of IF3 contacts the tRNA, whereas the C-terminal domain is bound to the platform of the 30S subunit. Binding of initiation factors and fMet-tRNAfMet induces a rotation of the head relative to the body of the 30S subunit, which is likely to prevail through 50S subunit joining until GTP hydrolysis and dissociation of IF2 take place. The structure provides insights into the mechanism of mRNA selection during translation initiation.

Desmosomes are intercellular adhesive junctions that impart strength to vertebrate tissues. Their dense, ordered intercellular attachments are formed by desmogleins (Dsgs) and desmocollins (Dscs), but the nature of trans-cellular interactions between these specialized cadherins is unclear. Here, using solution biophysics and coated-bead aggregation experiments, we demonstrate family-wise heterophilic specificity: All Dsgs form adhesive dimers with all Dscs, with affinities characteristic of each Dsg:Dsc pair. Crystal structures of ectodomains from Dsg2 and Dsg3 and from Dsc1 and Dsc2 show binding through a strand-swap mechanism similar to that of homophilic classical cadherins. However, conserved charged amino acids inhibit Dsg:Dsg and Dsc:Dsc interactions by same-charge repulsion and promote heterophilic Dsg:Dsc interactions through oppositecharge attraction. These findings show that Dsg:Dsc heterodimers represent the fundamental adhesive unit of desmosomes and provide a structural framework for understanding desmosome assembly. Dysfunction of desmosomes in inherited and acquired human diseases as well as in mouse genetic ablation studies causes characteristic defects in heart muscle and skin (3-5), demonstrating their importance in tissues that undergo mechanical stress. In electron micrographs, the hallmarks of mature desmosomes include a constant intermembrane distance of 280-340 Å, and apparently ordered electron-density in the intercellular space, often with a discrete midline connected by periodic cross-bridges to the cell membranes (6-9). The intercellular attachments of desmosomes are composed of transmembrane proteins from two specialized cadherin subfamilies: desmocollins (Dscs) and desmogleins (Dsgs). The human genome encodes three Dsc (Dsc1-Dsc3) and four Dsg (Dsg1-Dsg4) proteins, which share an overall domain organization comprising four to five extracellular cadherin (EC) domains, a single-pass transmembrane region, and an intracellular domain that binds to intermediate filaments via adaptor proteins desmoplakin and plakoglobin (1). Individual Dsgs and Dscs show differential expression patterns: Dsg2 and Dsc2 are expressed widely in all desmosome-forming tissues (1), whereas other desmosomal cadherins are expressed specifically in stratified epithelia with graded, overlapping patterns (1, 10). Notably, both Dscs and Dsgs appear necessary for adhesion in transfected cells (1,(11)(12)(13), and loss of either in genetic experiments causes loss of normal desmosomal adhesion (5,14,15).Although the ultrastructure of desmosomes is well characterized, a molecular-level understanding of the binding interactions between desmosomal cadherin extracellular regions that assemble these junctions has remained elusive. In particular, whether desmosomal cadherins have homophilic preferences or whether interactions occur between heterophilic pairs has been a matter of dispute (1,(11)(12)(13)(16)(17)(18). Electron tomography studies of native desmosomes (7, 8) have revealed cadherins binding through their EC1 domains...

Pyruvate carboxylase (PC) is a conserved metabolic enzyme with important cellular functions. We report here crystallographic and cryoEM studies of S. aureus PC (SaPC) in complex with acetyl-CoA, an allosteric activator, as well as mutagenesis, biochemical and structural studies of the biotin binding site of its carboxyltransferase (CT) domain. The disease-causing A610T mutation abolishes catalytic activity by blocking biotin binding to the CT active site, and Thr908 may play a catalytic role in the CT reaction. The crystal structure of SaPC in complex with CoA reveals a symmetrical tetramer, with one CoA molecule bound to each monomer, and cryoEM studies confirm the symmetrical nature of the tetramer. These observations are in sharp contrast to the highly asymmetrical tetramer of R. etli PC in complex with ethyl-CoA. Our structural information suggests that acetyl-CoA promotes a conformation for the dimer of the biotin carboxylase domain of PC that may be catalytically more competent.

Summary Although lysine acetylation is now recognized as a general protein modification for both histones and non-histone proteins1-3, the mechanisms of acetylation mediated actions are not completely understood. Acetylation of the C-terminal domain (CTD) of p53 was the first example for non-histone protein acetylation4. Yet the precise role of the CTD acetylation remains elusive. Lysine acetylation often creates binding sites for bromodomain-containing “reader” proteins5,6; surprisingly, in a proteomic screen, we identified SET as a major cellular factor whose binding with p53 is totally dependent on the CTD acetylation status. SET profoundly inhibits p53 transcriptional activity in unstressed cells but SET-mediated repression is completely abolished by stress-induced p53 CTD acetylation. Moreover, loss of the interaction with SET activates p53, resulting in tumor regression in mouse xenograft models. Notably, the acidic domain of SET acts as a “reader” for unacetylated CTD of p53 and this mechanism of acetylation-dependent regulation is widespread in nature. For example, p53 acetylation also modulates its interactions with similar acidic domains found in other p53 regulators including VPRBP, DAXX and PELP1 (refs. 7-9), and computational analysis of the proteome identified numerous proteins with the potential to serve as the acidic domain readers and lysine-rich ligands. Unlike bromodomain readers, which preferentially bind the acetylated forms of their cognate ligands, the acidic domain readers specifically recognize the unacetylated forms of their ligands. Finally, the acetylation-dependent regulation of p53 was further validated in vivo by using a knockin mouse model expressing an acetylation-mimicking form of p53. These results reveal that the acidic domain-containing factors act as a new class of acetylation-dependent regulators by targeting p53 and potentially, beyond.

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SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) is a novel virus of the family Coronaviridae. The virus causes the infectious disease COVID-19. The biology of coronaviruses has been studied for many years. However, bioinformatics tools designed explicitly for SARS-CoV-2 have only recently been developed as a rapid reaction to the need for fast detection, understanding and treatment of COVID-19. To control the ongoing COVID-19 pandemic, it is of utmost importance to get insight into the evolution and pathogenesis of the virus. In this review, we cover bioinformatics workflows and tools for the routine detection of SARS-CoV-2 infection, the reliable analysis of sequencing data, the tracking of the COVID-19 pandemic and evaluation of containment measures, the study of coronavirus evolution, the discovery of potential drug targets and development of therapeutic strategies. For each tool, we briefly describe its use case and how it advances research specifically for SARS-CoV-2. All tools are free to use and available online, either through web applications or public code repositories. Contact:  evbc@unj-jena.de