SUMMARY Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the causative agent of COVID-19 pandemic, which has caused a devastating global health crisis. The emergence of highly transmissible novel viral strains that escape neutralizing responses emphasizes the urgent need to deepen our understanding of SARS-CoV-2 biology and to develop additional therapeutic strategies. Using a comprehensive identification of RNA binding proteins (RBP) by mass spectrometry (ChIRP-M/S) approach, we identified 142 high-confidence cellular factors that bind the SARS-CoV-2 viral genome during infection. By systematically knocking down their expression in a human lung epithelial cell line, we found that the majority of the RBPs identified in our study are proviral factors that regulate SARS-CoV-2 genome replication. We showed that some of these proteins represented drug targets of interest for inhibiting SARS-CoV-2 infection. In conclusion, this study provides a comprehensive view of the SARS-CoV-2 RNA interactome during infection and highlights candidates for host-centered antiviral therapies.
Hepatitis C virus (HCV) is a major cause of liver disease in humans. The CD81 tetraspanin is necessary but not sufficient for HCV penetration into hepatocytes, and it was recently reported that the tight junction protein claudin-1 is a critical HCV entry cofactor. Here, we confirm the role of claudin-1 in HCV entry. In addition, we show that claudin-6 and claudin-9 expressed in CD81(+) cells also enable the entry of HCV pseudoparticles derived from six of the major genotypes. Whereas claudin-1, -6, and -9 function equally well as entry cofactors in endothelial cells, claudin-1 is more efficient in hepatoma cells. This suggests that additional cellular factors modulate the ability of claudins to function as HCV entry cofactors. Our work has generated novel and essential means to investigate the mechanism of HCV penetration into hepatocytes and the role of the claudin protein family in HCV dissemination, replication, and pathogenesis.
The ubiquitin ligase CBLL1 (also known as HAKAI) has been proposed to be a critical cellular factor exploited by West Nile virus (WNV) for productive infection. CBLL1 has emerged as a major hit in a recent RNA interference screen designed to identify cellular factors required for the early stages of the WNV life cycle. Follow-up experiments showed that HeLa cells knocked down for CBLL1 by a small interfering RNA (siRNA) failed to internalize WNV particles and resisted infection. Furthermore, depletion of a free-ubiquitin pool by the proteasome inhibitor MG132 abolished WNV endocytosis, suggesting that CBLL1 acts in concert with the ubiquitin proteasome system to mediate virus internalization. Here, we examined the effect of CBLL1 knockdown and proteasome inhibitors on infection by WNV and other flaviviruses. We identified new siRNAs that repress the CBLL1 protein and strongly inhibit the endocytosis of Listeria monocytogenes, a bacterial pathogen known to require CBLL1 to invade host cells. Strikingly, however, we detected efficient WNV, dengue virus, and yellow fever virus infection of human cells, despite potent downregulation of CBLL1 by RNA interference. In addition, we found that the proteasome inhibitors MG132 and lactacystin did not affect WNV internalization but strongly repressed flavivirus RNA translation and replication. Together, these data do not support a requirement for CBLL1 during flavivirus entry and rather suggest an essential role of the ubiquitin/proteasome pathway for flavivirus genome amplification.
A serological survey for human T cell leukaemia virus (HTLV)/simian T cell leukaemia virus (STLV) antibodies was performed in 61 wild-caught African apes, including five gorillas and 56 chimpanzees originating from south Cameroon. Two young animals, a gorilla (Gorilla gorilla gorilla) and a chimpanzee (Pan troglodytes vellerosus), exhibited a pattern of complete HTLV-I seroreactivity. Sequence comparison and phylogenetic analyses using the complete LTR (750 bp) and a 522 bp fragment of the env gene indicated the existence of two novel STLV-I strains, both of which belonged to HTLV-I/STLV-I molecular clade subtype B, specific to central Africa. These first STLV-I strains to be characterized in gorilla and chimpanzee were closely related to each other as well as to several HTLV-I strains originating from inhabitants of south Cameroon, including pygmies. Such findings reinforce the hypothesis of interspecies transmission of STLV-I to humans, leading to the present day distribution of HTLV-I in central African inhabitants.
Full-genome sequencing and analysis of the highly divergent simian T-cell lymphotropic virus type 1 (STLV-1) strain MarB43 in Macaca arctoides indicated that its open reading frame structure is compatible with proper functioning of its Gag, Pol, Env, Tax and Rex proteins. Detailed analysis of the coding potential, however, revealed that MarB43 is probably forced to use the human T-cell lymphotropic virus type 2/STLV-2 env - tax - rex splice-acceptor homologue and that the proximal pX auxiliary proteins p12 I , p13 II , p30 II and p27 I seem to have lost their function. Full-genome ( gag - pol - env - tax ), long terminal repeat and env phylogenetic analyses conclusively identified STLV-1 in M. arctoides as the currently most divergent STLV-1 strain. The long branching pattern of the monophyletic STLV-1 Macaca subspecies clades suggests that macaques might be the ancestral reservoir for primate T-cell lymphotropic virus type 1 in Asia. Full-genome molecular-clock analysis supports an archaic introduction of STLV-1 on the Asian continent, at least 269 000–156 000 years ago.
(Cell Reports 21, 3900–3913, December 26, 2017) In the originally published version of this article, Figure S1 in the Supplemental Information became unreadable during the production process. Figure S1 has now been corrected online. The Cell Reports team regrets this error. A Global Interactome Map of the Dengue Virus NS1 Identifies Virus Restriction and Dependency Host FactorsHafirassou et al.Cell ReportsDecember 26, 2017In BriefIn this study, Hafirassou et al. provide a global proteomic analysis of the cellular factors associated with the DENV NS1 protein. They reveal a network of host cellular processes hijacked by DENV and identify multiple host factors that facilitate or restrict virus infection. Full-Text PDF Open Access
