title: The human papillomavirus type 16 E7 protein is associated with the nucleolus in mammalian and yeast cells.
abstract: In this study we show, by immunofluorescence and electron microscopy immuno-gold labelling, that the major transforming protein of Human Papillomavirus type 16 E7 is associated with the nucleolus of cells derived from the HPV16-positive cervical carcinoma line CaSki. The E7 nucleolar staining appeared to be cell cycle dependent, being considerably reduced in the G2 phase. The total level of the protein in the cell, however, remained constant during all phases. We also show that the cellular protein Rb1, which is targeted by E7, is localised in the nucleus and nucleolus in CaSki cells. Thus, it is possible that the presence of E7 in the nucleolus correlates with a hypothetical function(s) of Rb1 in this particular intranuclear compartment. The nucleolar localisation of HPV16 E7 protein was also observed in the fission yeast Schizosaccharomyces pombe, suggesting that a targeting mechanism of HPV16 E7 protein into the nucleolus is common to both mammalian and yeast systems. Nucleolar localisation of HPV16 E7 protein may be independent from Rb1 since no Rb1 related proteins have been identified in fission yeast.
authors.affiliation: Biomedizinische Strukturforschung, Deutsches Krebsforschungszentrum, INF 242, Heidelberg, Germany.
authors.forename: O
authors.initials: O
authors.lastname: Zatsepina
authors.forename: J
authors.initials: J
authors.lastname: Braspenning
authors.forename: D
authors.initials: D
authors.lastname: Robberson
authors.forename: M A
authors.initials: MA
authors.lastname: Hajibagheri
authors.forename: K J
authors.initials: KJ
authors.lastname: Blight
authors.forename: S
authors.initials: S
authors.lastname: Ely
authors.forename: M
authors.initials: M
authors.lastname: Hibma
authors.forename: D
authors.initials: D
authors.lastname: Spitkovsky
authors.forename: M
authors.initials: M
authors.lastname: Trendelenburg
authors.forename: L
authors.initials: L
authors.lastname: Crawford
authors.forename: M
authors.initials: M
authors.lastname: Tommasino
mesh_terms: D000911:Antibodies, Monoclonal; D002453:Cell Cycle / Q000502:physiology; D002466:Cell Nucleolus / Q000378:metabolism*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D009856:Oncogene Proteins, Viral / Q000378:metabolism*; D012097:Repressor Proteins; D016160:Retinoblastoma Protein / Q000032:analysis; D012568:Schizosaccharomyces / Q000378:metabolism* / Q000648:ultrastructure; D014407:Tumor Cells, Cultured; D002583:Uterine Cervical Neoplasms / Q000378:metabolism* / Q000473:pathology / Q000648:ultrastructure
chemical_list: D000911:Antibodies, Monoclonal; C068651:E6 protein, Human papillomavirus type 16; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D016160:Retinoblastoma Protein