title: Virion assembly factories in the nucleus of polyomavirus-infected cells.
abstract: Most DNA viruses replicate in the cell nucleus, although the specific sites of virion assembly are as yet poorly defined. Electron microscopy on freeze-substituted, plastic-embedded sections of murine polyomavirus (PyV)-infected 3T3 mouse fibroblasts or mouse embryonic fibroblasts (MEFs) revealed tubular structures in the nucleus adjacent to clusters of assembled virions, with virions apparently "shed" or "budding" from their ends. Promyelocytic leukemia nuclear bodies (PML-NBs) have been suggested as possible sites for viral replication of polyomaviruses (BKV and SV40), herpes simplex virus (HSV), and adenovirus (Ad). Immunohistochemistry and FISH demonstrated co-localization of the viral T-antigen (Tag), PyV DNA, and the host DNA repair protein MRE11, adjacent to the PML-NBs. In PML⁻/⁻ MEFs the co-localization of MRE11, Tag, and PyV DNA remained unchanged, suggesting that the PML protein itself was not responsible for their association. Furthermore, PyV-infected PML⁻/⁻ MEFs and PML⁻/⁻ mice replicated wild-type levels of infectious virus. Therefore, although the PML protein may identify sites of PyV replication, neither the observed "virus factories" nor virus assembly were dependent on PML. The ultrastructure of the tubes suggests a new model for the encapsidation of small DNA viruses.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, University of Colorado, Boulder, Colorado, United States of America.
authors.forename: Kimberly D
authors.initials: KD
authors.lastname: Erickson
authors.forename: Cedric
authors.initials: C
authors.lastname: Bouchet-Marquis
authors.forename: Katie
authors.initials: K
authors.lastname: Heiser
authors.forename: Eva
authors.initials: E
authors.lastname: Szomolanyi-Tsuda
authors.forename: Rabinarayan
authors.initials: R
authors.lastname: Mishra
authors.forename: Benjamin
authors.initials: B
authors.lastname: Lamothe
authors.forename: Andreas
authors.initials: A
authors.lastname: Hoenger
authors.forename: Robert L
authors.initials: RL
authors.lastname: Garcea
mesh_terms: D016475:3T3 Cells; D000818:Animals; D002467:Cell Nucleus / Q000235:genetics / Q000378:metabolism / Q000821:virology*; D045643:DNA Repair Enzymes / Q000235:genetics / Q000378:metabolism; D004279:DNA, Viral / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004622:Embryo, Mammalian / Q000378:metabolism / Q000473:pathology / Q000821:virology; D005347:Fibroblasts / Q000378:metabolism / Q000473:pathology / Q000821:virology; D000076228:MRE11 Homologue Protein; D051379:Mice; D018345:Mice, Knockout; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D011120:Polyomavirus / Q000502:physiology*; D027601:Polyomavirus Infections / Q000235:genetics / Q000378:metabolism*; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025521:Tumor Suppressor Proteins / Q000235:genetics / Q000378:metabolism*; D019065:Virus Assembly / Q000502:physiology*
chemical_list: D004279:DNA, Viral; D004268:DNA-Binding Proteins; C512689:Mre11a protein, mouse; D009687:Nuclear Proteins; C513293:Pml protein, mouse; D000071156:Promyelocytic Leukemia Protein; D014157:Transcription Factors; D025521:Tumor Suppressor Proteins; D000076228:MRE11 Homologue Protein; D045643:DNA Repair Enzymes