A North American Arenavirus Uses Human Transferrin Receptor
North American arenaviruses are generally considered nonpathogenic unlike the related New World arenaviruses that cause hemorrhagic fever. Moreover, New World arenaviruses with the capacity to engage human transferrin receptor 1 (TfR1) are more virulent compared with nonbinding strains. Zong et al. (p. 9418–9428) demonstrate that one North American arenavirus isolate closely related to Whitewater Arroyo virus, which has been implicated in fatal human cases, uses human TfR1 for attachment and entry. Additionally, modest changes in human TfR1 are sufficient to convert human TfR1 into a functional receptor for most North American arenaviruses. These findings suggest that North American arenaviruses have a greater potential to emerge as human pathogens than previously appreciated.
Sumoylation of Influenza A Virus Nucleoprotein Is Essential for Intracellular Trafficking and Virus Replication
Influenza A virus exploits the host sumoylation machinery to modify its viral proteins, but the functional outcomes of viral sumoylation are not well understood. Han et al. (p. 9379–9390) demonstrate that influenza A virus nucleoprotein (NP) is a new sumoylation target. This modification is conserved among different influenza A virus subtypes and strains. Additionally, sumoylation of NP modulates intracellular NP trafficking and is essential for virus replication. This study suggests that influenza A virus relies on sumoylation to productively infect target cells.
Human Cytomegalovirus Proteins Are Required for Remodeling the Cellular Secretory Apparatus
Human cytomegalovirus (HCMV) remodels the cellular secretory apparatus to facilitate generation of the cytoplasmic virion assembly complex (cVAC). Yet, the HCMV proteins that regulate the cVAC are not known. Using small interfering RNA technology, Das and Ortiz et al. (p. 9086–9099) identified HCMV genes UL48, UL94, and UL103 as mediators of cVAC development. This work enhances an understanding of HCMV virion assembly and highlights potential antiviral targets.
Hepatitis B Virus Glycosylation, a Balance between Competing Functions
Glycosylated and nonglycosylated isoforms of the envelope proteins of hepatitis B virus are usually present on the virion surface. Julithe et al. (p. 9049–9059) show that glycosylation has a positive effect on virion assembly and immune escape. However, glycosylation has a detrimental effect on viral infectivity. Thus, partial glycosylation of the hepatitis B virus surface proteins reflects a fine-tuned balance between these competing functions.
Extraribosomal Function of Ribosomal Protein L13a in Antiviral Defense
The host immune system is capable of deploying a variety of antiviral defense mechanisms. Mazumder et al. (p. 9100–9110) show that ribosomal protein L13a is released from host cell ribosomes soon after respiratory syncytial virus (RSV) infection. Upon ribosomal release, L13a binds to a target sequence in the RSV matrix gene mRNA and prevents synthesis of the matrix protein, thereby reducing viral replication. This study illuminates a previously unappreciated mechanism of host defense and may facilitate design of RSV antiviral agents.
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- A North American Arenavirus Uses Human Transferrin Receptor
- Sumoylation of Influenza A Virus Nucleoprotein Is Essential for Intracellular Trafficking and Virus Replication
- Human Cytomegalovirus Proteins Are Required for Remodeling the Cellular Secretory Apparatus
- Hepatitis B Virus Glycosylation, a Balance between Competing Functions
- Extraribosomal Function of Ribosomal Protein L13a in Antiviral Defense
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