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Publication Abstract from PubMed

JC polyomavirus (JCPyV) infection of immunocompromised individuals results in the fatal demyelinating disease progressive multifocal leukoencephalopathy (PML). The viral capsid of JCPyV is composed primarily of the major capsid protein, virus protein 1 (VP1), and pentameric arrangement of VP1 monomers results in the formation of a pore at the five-fold axis of symmetry. While the presence of this pore is conserved among polyomaviruses, its functional role in infection or assembly is unknown. Here, we investigate the role of the five-fold pore in assembly and infection of JCPyV by generating a panel of mutant viruses containing amino acid substitutions to the residues lining this pore. Multicycle growth assays demonstrated that the relative fitness of all mutants was reduced, as compared to wild type virus. Bacterial expression of VP1 pentamers containing substitutions to residues lining the five-fold pore did not affect pentamer assembly or prevent association with the minor capsid protein VP2. The X-ray crystal structures of selected pore mutants contained subtle changes to the five-fold pore, and no other changes to VP1 were observed. Pore-mutant pseudoviruses were not deficient in assembly, packaging of the minor capsid proteins, binding to cells, or in transport to the host cell endoplasmic reticulum. Instead, these mutant viruses were unable to expose VP2 upon arrival to the endoplasmic reticulum, a step that is critical for infection. This study demonstrates that the five-fold pore is an important structural feature of JCPyV and minor modifications to this structure has significant impacts on infectious entry. IMPORTANCE: JCPyV is an important human pathogen that causes a severe neurological disease in immunocompromised individuals. While the high resolution X-ray structure of the major capsid protein of JCPyV has been solved, the importance of a major structural feature of the capsid, the five-fold pore, remains poorly understood. This pore is conserved across polyomaviruses and suggests that these viruses have either limited structural plasticity in this region or that this pore is important in infection or assembly. Using a structure-guided mutational approach, we showed that modulation of this pore severely inhibits JCPyV infection. These mutants do not appear deficient in assembly or early steps in infectious entry and are instead reduced in their ability to expose a minor capsid protein in the host cell endoplasmic reticulum. Our work demonstrates that the five-fold pore is an important structural feature for JCPyV.

Modulation of a pore in the capsid of JC polyomavirus reduces infectivity and prevents exposure of the minor capsid proteins.,Nelson CD, Stroh LJ, Gee GV, O'Hara BA, Stehle T, Atwood WJ J Virol. 2015 Jan 21. pii: JVI.00089-15. PMID:25609820^[2]

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.