Lassa virus spreads from rodents to humans and can lead to lethal hemorrhagic fever. Despite its broad tropism, chicken cells were reported to resist infection thirty years ago. We show that Lassa virus readily engaged its cell surface receptor α-dystroglycan in avian cells, but virus entry in susceptible species involved a pH-dependent switch to an intracellular receptor, the lysosome-resident protein LAMP1. Iterative haploid screens revealed that the sialyltransferase ST3GAL4 was required for the interaction of the virus glycoprotein with LAMP1. A single glycosylated residue in LAMP1, present in susceptible species but absent in birds, was essential for interaction with the Lassa virus envelope protein and subsequent infection. The resistance of Lamp1-deficient mice to Lassa virus highlights the relevance of this receptor switch in vivo.

Summary Arenaviruses cause fatal haemorrhagic disease in humans. Old-World arenavirus glycoproteins (GPs) mainly engage α-dystroglycan as a cell surface receptor, while New-World arenaviruses hijack transferrin receptor. However, the Lujo virus (LUJV) glycoprotein does not cluster with New-or Old-world arenaviruses. Using a recombinant vesicular stomatitis virus containing LUJV glycoprotein (LUJV GP) as its sole attachment and fusion protein (VSV-LUJV), we demonstrate that infection is independent of known arenavirus receptor genes. A genome-wide haploid genetic screen identified the transmembrane protein neuropilin 2 (NRP2) and tetraspanin CD63 as factors for LUJV GP-mediated infection. LUJV GP binds the N-terminal domain of NRP2, while CD63 stimulates pH-activated LUJV GP-mediated membrane fusion. Overexpression of NRP2 or its N-terminal domain enhances VSV-LUJV infection, and cells lacking NRP2 are deficient in wild-type LUJV infection. These findings uncover this distinct set of host cell entry factors in LUJV infection and are attractive focus points for therapeutic intervention.

No abstract

TREX is a conserved multiprotein complex that is necessary for efficient mRNA export to the cytoplasm. In Saccharomyces cerevisiae, the TREX complex is additionally implicated in RNA quality control pathways, but it is unclear whether this function is conserved in mammalian cells. The Kaposi's sarcoma-associated herpesvirus (

Pre-mRNA processing is mechanistically linked to transcription with RNA pol II serving as a platform to recruit RNA processing factors to nascent transcripts. The TREX complex member, REF/Aly, has been suggested to play roles in transcription and nuclear RNA stability in addition to its more broadly characterized role in mRNA export. We employed RNA-seq to identify a subset of transcripts with decreased expression in both nuclear and cytoplasmic fractions upon REF/Aly knockdown, which implies that REF/Aly affects their expression upstream of its role in mRNA export. Transcription inhibition experiments and metabolic labeling assays argue that REF/Aly does not affect stability of selected candidate transcripts. Instead, ChIP assays and nuclear run-on analysis reveal that REF/Aly depletion diminishes the transcription of these candidate genes. Furthermore, we determined that REF/Aly binds directly to candidate transcripts, supporting a direct effect of REF/Aly on candidate gene transcription. Taken together, our data suggest that the importance of REF/Aly is not limited to RNA export, but that REF/Aly is also critical for gene expression at the level of transcription. Our data are consistent with the model that REF/Aly is involved in linking splicing with transcription efficiency.