The novel coronavirus SARS-CoV-2, the causative agent of COVID-19 respiratory disease, has infected over 2.3 million people, killed over 160,000, and caused worldwide social and economic disruption 1,2 . There are currently no antiviral drugs with proven clinical efficacy, nor are there vaccines for its prevention, and these efforts are hampered by limited knowledge of the molecular details of SARS-CoV-2 infection. To address this, we cloned, tagged and expressed 26 of the 29 SARS-CoV-2 proteins in human cells and identified the human proteins physically associated with each using affinity-purification mass spectrometry (AP-MS), identifying 332 high-confidence SARS-CoV-2-human protein-protein interactions (PPIs). Among these, we identify 66 druggable human proteins or host factors targeted by 69 compounds (29 FDA-approved drugs, 12 drugs in clinical trials, and 28 preclinical compounds). Screening a subset of these in multiple viral assays identified two sets of pharmacological agents that displayed antiviral activity: inhibitors of mRNA translation and predicted regulators of the Sigma1 and Sigma2 receptors. Further studies of these host factor targeting agents, including their combination with drugs that directly target viral enzymes, could lead to a therapeutic regimen to treat COVID-19.

Here we report the use of random activation of gene expression (RAGE) to create genome-wide protein expression libraries. RAGE libraries containing only 5 x 10(6) individual clones were found to express every gene tested, including genes that are normally silent in the parent cell line. Furthermore, endogenous genes were activated at similar frequencies and expressed at similar levels within RAGE libraries created from multiple human cell lines, demonstrating that RAGE libraries are inherently normalized. Pools of RAGE clones were used to isolate 19,547 human gene clusters, approximately 53% of which were novel when tested against public databases of expressed sequence tag (EST) and complementary DNA (cDNA). Isolation of individual clones confirmed that the activated endogenous genes can be expressed at high levels to produce biologically active proteins. The properties of RAGE libraries and RAGE expression clones are well suited for a number of biotechnological applications including gene discovery, protein characterization, drug development, and protein manufacturing.

The protein Gcn1 (General control non-derepressible 1) is found in virtually all eukaryotes, and is a key component of the general amino acid control signal transduction pathway. This pathway is best known for its importance for cells to sense and overcome amino acid starvation. Gcn1 directly binds to the RWD (RING finger-containing proteins, WD-repeat-containing proteins, and yeast DEAD (DEXD)-like helicases) domain of the protein kinase Gcn2, and this is essential for delivering the starvation signal to Gcn2. Gcn2, and thus the GAAC (General Amino Acid Control) pathway, then becomes activated enabling the cell to cope and overcome the starvation condition. Using sensitive homology detection and fold recognition methods a conserved structural domain in Gcn1, RWD Binding Domain (RWDBD), has been recognized that encompasses the region experimentally shown previously to be involved in Gcn2 binding. Further, the structural fold for this domain has been recognized as the ARM (Armadillo) domain, and residues likely to be involved in the binding of Gcn2 RWD domain have been identified within this structural domain. Thus, the current analysis provides a structural basis of Gcn1-Gcn2 association.ReviewersThis article was reviewed by Dr Oliviero Carugo and Dr Michael Gromiha.Electronic supplementary materialThe online version of this article (doi:10.1186/s13062-017-0184-3) contains supplementary material, which is available to authorized users.