Journal of Virology, November 2009, p. 10845, Vol. 83, No. 21
0022-538X/09/$08.00+0 doi:10.1128/JVI.01906-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
| SPOTLIGHT |
Articles of Significant Interest Selected from This Issue by the Editors
Not Just a Vehicle: Uncoating Low-Density Lipoprotein Receptor Assists Human RhinovirusICAM-1, the receptor of major group human rhinoviruses (HRVs), possesses "catalytic" activity as it triggers viral uncoating. No such function was known for the low-density lipoprotein receptor (LDLR), which internalizes minor group HRVs. Konecsni et al. (p. 10922-10930) now demonstrate that the β-propeller domain of LDLR also aids uncoating by triggering release of the virus in the acidic environment of endosomes. LDLR thus combines high-affinity multimodular binding with a unique release mechanism.
Insight into the Triggering Mechanism for Paramyxovirus Fusion
Paramyxovirus entry requires an attachment protein (HN, H, or G) that binds to a cellular receptor and a fusion protein (F) that drives membrane merger. How a signal is transmitted from HN to F to trigger fusion is unclear. Connolly et al. (p. 10857-10868) use bimolecular fluorescence complementation to distinguish between two hypothetical models of fusion activation. This work supports a provocateur model of activation, wherein HN destabilizes F to trigger fusion after receptor binding and provides evidence contrary to a clamp model, wherein HN stabilizes F in its pre-fusion state and triggers fusion by releasing F.
SSRP1 Contributes to LANA-Dependent DNA Replication of Kaposi's Sarcoma-Associated Virus
Despite the requirement for ORC and MCM proteins, it is not known whether additional cellular proteins contribute to latent DNA replication of Kaposi's sarcoma-associated virus (KSHV). Hu et al. (p. 11051-11063) used genetic and proteomics approaches to identify SSRP1, a subunit of the chromatin remodeling factor FACT, as a cellular protein that forms a complex with KSHV latency-associated nuclear antigen (LANA) at the origin region in a cell-cycle dependent manner and contributes to LANA-dependent DNA replication. These results suggest that LANA recruits SSRP1 and forms a specific virus-chromatin remodeling platform that supports viral DNA replication during latency.
Overproduction of Subviral Particles Is Not Essential for Hepatitis B Virus Virion Formation
Hepatitis B virus is unique among enveloped viruses in its robust secretion of envelope proteins as nucleocapsid-free subviral particles. These subviral particles exceed virions by at least 1,000-fold. Garcia et al. (p. 11152-11165) used trans-complementation assays and mutant constructs to demonstrate that limiting envelope protein expression selectively diminished secretion of subviral particles but did not alter the yield of virions. This finding leaves open other potential functions of subviral particles, such as induction of immune tolerance in neonates.
Structural Basis of Human Immunodeficiency Virus Type 1 Neutralization Resistance
The region of human immunodeficiency virus type 1 (HIV-1) attachment protein gp120 that contacts its primary receptor CD4 is functionally conserved and vulnerable to neutralizing antibodies. However, some strains of HIV-1 can evade neutralizing antibodies directed against this CD4-binding region. Wu et al. (p. 10892-10907) used structural modeling and mutagenesis experiments to show that resistance to a CD4-binding-site antibody occurs when key contact amino acids are altered that impair antibody binding but not gp120 binding to CD4. These findings explain how HIV-1 evades neutralization yet retains the capacity to bind its primary cellular receptor.
Journal of Virology, November 2009, p. 10845, Vol. 83, No. 21
0022-538X/09/$08.00+0 doi:10.1128/JVI.01906-09
Copyright © 2009, American Society for Microbiology. All Rights Reserved.
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