Identification of a nuclear export signal sequence for bovine papillomavirus E1 protein.
Recent studies have demonstrated nuclear export by papillomavirus E1 proteins, but the requisite export sequence(s) for bovine papillomavirus (BPV) E1 were not defined. In this report we identify three functional nuclear export sequences (NES) present in BPV E1, with NES2 being the strongest in reporter assays. Nuclear localization of BPV1 E1 was modulated by over- or under-expression of CRM1, the major cellular exportin, and export was strongly reduced by the CRM1 inhibitor, Leptomycin B, indicating that E1 export occurs primarily through a CRM1-dependent process. Consistent with the in vivo functional results, E1 bound CRM1 in an in vitro pull-down assay. In addition, sumoylated E1 bound CRM1 more effectively than unmodified E1, suggesting that E1 export may be regulated by SUMO modification. Lastly, an E1 NES2 mutant accumulated in the nucleus to a greater extent than wild-type E1, yet was defective for viral origin replication in vivo. However, NES2 exhibited no intrinsic replication defect in an in vitro replication assay, implying that nucleocytoplasmic shuttling may be required to maintain E1 in a replication competent state.
Rosas-Acosta
Germán
G
Department of Molecular and Microbial Pathogenesis, Texas A&M Health Science Center, College of Medicine, College Station, TX 77843-1114, USA.
Wilson
Van G
VG
D021581:Active Transport, Cell Nucleus; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D016466:CHO Cells; D019556:COS Cells; D002417:Cattle; D002467:Cell Nucleus / Q000378:metabolism; D002522:Chlorocebus aethiops; D006224:Cricetinae; D003412:Cricetulus; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D028884:Karyopherins / Q000378:metabolism; D008969:Molecular Sequence Data; D049790:Nuclear Export Signals / Q000235:genetics* / Q000502:physiology; D019913:Nuclear Localization Signals; D018160:Receptors, Cytoplasmic and Nuclear / Q000378:metabolism; D025842:SUMO-1 Protein; D014764:Viral Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000097606:Exportin 1 Protein
D004268:DNA-Binding Proteins; D028884:Karyopherins; D049790:Nuclear Export Signals; D019913:Nuclear Localization Signals; D018160:Receptors, Cytoplasmic and Nuclear; D025842:SUMO-1 Protein; D014764:Viral Proteins; D000097606:Exportin 1 Protein; C069814:E1 protein, Bovine papillomavirus