title: Importin-beta family members mediate alpharetrovirus gag nuclear entry via interactions with matrix and nucleocapsid.
abstract: The retroviral Gag polyprotein orchestrates the assembly and release of virus particles from infected cells. We previously reported that nuclear transport of the Rous sarcoma virus (RSV) Gag protein is intrinsic to the virus assembly pathway. To identify cis- and trans-acting factors governing nucleocytoplasmic trafficking, we developed novel vectors to express regions of Gag in Saccharomyces cerevisiae. The localization of Gag proteins was examined in the wild type and in mutant strains deficient in members of the importin-beta family. We confirmed the Crm1p dependence of the previously identified Gag p10 nuclear export signal. The known nuclear localization signal (NLS) in MA (matrix) was also functional in S. cerevisiae, and additionally we discovered a novel NLS within the NC (nucleocapsid) domain of Gag. MA utilizes Kap120p and Mtr10p import receptors while nuclear entry of NC involves the classical importin-alpha/beta (Kap60p/95p) pathway. NC also possesses nuclear targeting activity in avian cells and contains the primary signal for the import of the Gag polyprotein. Thus, the nucleocytoplasmic dynamics of RSV Gag depend upon the counterbalance of Crm1p-mediated export with two independent NLSs, each interacting with distinct nuclear import factors.
authors.affiliation: Division of Infectious Diseases HO36, Penn State College of Medicine, 500 University Drive, Hershey, PA 17033, USA.
authors.forename: Kristin L
authors.initials: KL
authors.lastname: Butterfield-Gerson
authors.forename: Lisa Z
authors.initials: LZ
authors.lastname: Scheifele
authors.forename: Eileen P
authors.initials: EP
authors.lastname: Ryan
authors.forename: Anita K
authors.initials: AK
authors.lastname: Hopper
authors.forename: Leslie J
authors.initials: LJ
authors.lastname: Parent
mesh_terms: D001358:Avian Sarcoma Viruses / Q000502:physiology*; D017353:Gene Deletion; D015683:Gene Products, gag / Q000378:metabolism*; D005822:Genetic Vectors; D028884:Karyopherins / Q000378:metabolism / Q000502:physiology; D018613:Microscopy, Confocal; D009154:Mutation; D019913:Nuclear Localization Signals / Q000502:physiology; D019251:Nucleocapsid / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D016601:RNA-Binding Proteins / Q000378:metabolism; D018160:Receptors, Cytoplasmic and Nuclear / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000378:metabolism; D014763:Viral Matrix Proteins / Q000378:metabolism*; D028961:beta Karyopherins / Q000235:genetics / Q000502:physiology*; D000097606:Exportin 1 Protein
chemical_list: D015683:Gene Products, gag; D028884:Karyopherins; D019913:Nuclear Localization Signals; D029543:Nucleocytoplasmic Transport Proteins; D016601:RNA-Binding Proteins; D018160:Receptors, Cytoplasmic and Nuclear; D029701:Saccharomyces cerevisiae Proteins; D014763:Viral Matrix Proteins; D028961:beta Karyopherins; D000097606:Exportin 1 Protein; C479560:KAP120 protein, S cerevisiae; C110033:MTR10 protein, S cerevisiae