title: Nuclear export of African swine fever virus p37 protein occurs through two distinct pathways and is mediated by three independent signals.
abstract: Nucleocytoplasmic shuttling activity of the African swine fever virus p37 protein, a major structural protein of this highly complex virus, has been recently reported. The systematic characterization of the nuclear export ability of this protein constituted the major purpose of the present study. We report that both the N- and C-terminal regions of p37 protein are actively exported from the nucleus to the cytoplasm of yeast and mammalian cells. Moreover, experiments using leptomycin B and small interfering RNAs targeting the CRM1 receptor have demonstrated that the export of p37 protein is mediated by both the CRM1-dependent and CRM1-independent nuclear export pathways. Two signals responsible for the CRM1-mediated nuclear export of p37 protein were identified at the N terminus of the protein, and an additional signal was identified at the C-terminal region, which mediates the CRM1-independent nuclear export. Interestingly, site-directed mutagenesis revealed that hydrophobic amino acids are critical to the function of these three nuclear export signals. Overall, our results demonstrate that two distinct pathways contribute to the strong nuclear export of full-length p37 protein, which is mediated by three independent nuclear export signals. The existence of overlapping nuclear export mechanisms, together with our observation that p37 protein is localized in the nucleus at early stages of infection and exclusively in the cytoplasm at later stages, suggests that the nuclear transport ability of this protein may be critical to the African swine fever virus replication cycle.
authors.affiliation: Department of Biochemistry, Faculty of Sciences and Technology, University of Coimbra, Apartado 3126, 3001-401 Coimbra, Portugal.
authors.forename: Ana
authors.initials: A
authors.lastname: Eulálio
authors.forename: Isabel
authors.initials: I
authors.lastname: Nunes-Correia
authors.forename: Ana Luísa
authors.initials: AL
authors.lastname: Carvalho
authors.forename: Carlos
authors.initials: C
authors.lastname: Faro
authors.forename: Vitaly
authors.initials: V
authors.lastname: Citovsky
authors.forename: José
authors.initials: J
authors.lastname: Salas
authors.forename: Maria L
authors.initials: ML
authors.lastname: Salas
authors.forename: Sérgio
authors.initials: S
authors.lastname: Simões
authors.forename: Maria C Pedroso
authors.initials: MC
authors.lastname: de Lima
mesh_terms: D021581:Active Transport, Cell Nucleus; D000358:African Swine Fever Virus / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D028884:Karyopherins / Q000378:metabolism; D008969:Molecular Sequence Data; D019913:Nuclear Localization Signals; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D015398:Signal Transduction; D014709:Vero Cells; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014779:Virus Replication; D000097606:Exportin 1 Protein
chemical_list: D028884:Karyopherins; D019913:Nuclear Localization Signals; D018160:Receptors, Cytoplasmic and Nuclear; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins; D000097606:Exportin 1 Protein; C059340:protein p37, African swine fever virus