Highlights d 3,000 compounds screened in two cell types against SARS-CoV-2 d Entry pathways are distinct in hepatocyte Huh7.5 and respiratory Calu-3 cells d Only nine compounds that are active in Huh7.5 cells are active in Calu-3 cells d Cyclosporin and cyclophilin inhibitors block SARS-CoV-2 infection in diverse cells

c-Src, a non-receptor protein tyrosine kinase, activates NF-κB and STAT3, which in turn triggers the transcription of anti-apoptosis- and cell cycle-related genes. c-Src protein regulates cell proliferation, cell motility and programmed cell death. And the elevated level of activated c-Src protein is related with solid tumor generation. Translation of c-Src mRNA is directed by an IRES element which mediates persistent translation under stress conditions when translation of most mRNAs is inhibited by a phosphorylation of the alpha subunit of eIF2 carrying the initiator tRNA (tRNAi) to 40S ribosomal subunit under normal conditions. The molecular basis of the stress-resistant translation of c-Src mRNA remained to be elucidated. Here, we report that eIF2A, an alternative tRNAi carrier, is responsible for the stress-resistant translation of c-Src mRNA. eIF2A facilitates tRNAi loading onto the 40S ribosomal subunit in a c-Src mRNA-dependent manner. And a direct interaction between eIF2A and a stem-loop structure (SL I) in the c-Src IRES is required for the c-Src IRES-dependent translation under stress conditions but not under normal conditions. Finally, we showed that the eIF2A-dependent translation of c-Src mRNA plays a pivotal role in cell proliferation under stress conditions.

Hepatitis C virus (HCV) is a positive-strand RNA virus replicating in a membranous replication organelle composed primarily of double-membrane vesicles (DMVs) having morphological resemblance to autophagosomes. To define the mechanism of DMV formation and the possible link to autophagy, we conducted a yeast two-hybrid screening revealing 32 cellular proteins potentially interacting with HCV proteins. Among these was the Receptor for Activated Protein C Kinase 1 (RACK1), a scaffolding protein involved in many cellular processes, including autophagy. Depletion of RACK1 strongly inhibits HCV RNA replication without affecting HCV internal ribosome entry site (IRES) activity. RACK1 is required for the rewiring of subcellular membranous structures and for the induction of autophagy. RACK1 binds to HCV nonstructural protein 5A (NS5A), which induces DMV formation. NS5A interacts with ATG14L in a RACK1 dependent manner, and with the ATG14L-Beclin1-Vps34-Vps15 complex that is required for autophagosome formation. Both RACK1 and ATG14L are required for HCV DMV formation and viral RNA replication. These results indicate that NS5A participates in the formation of the HCV replication organelle through interactions with RACK1 and ATG14L.