title: Growth inhibition of HeLa cells is a conserved feature of high-risk human papillomavirus E8^E2C proteins and can also be achieved by an artificial repressor protein.
abstract: Infections with certain human papillomaviruses (HPV), such as type 16 (HPV16), 18, or 31, are a necessary risk factor for the development of cervical cancer. Transcript analyses of several HPV revealed that the viral E2 gene encodes both the E2 regulator protein and the E8∧E2C protein, which differ in their amino termini. Up to now, functional studies have focused on HPV31 E8∧E2C and demonstrated that it is a potent repressor of viral transcription and replication. However, recent analyses of HPV16 genomes have suggested that E8∧E2C proteins may differ in their activities. Therefore, we performed a comparative analysis of E8∧E2C proteins of HPV16, -18, and -31. All E8∧E2C proteins potently inhibited HPV E6/E7 oncogene promoters, and also displayed long-distance transcriptional-repression activities. Furthermore, the expression of all E8∧E2C proteins inhibited the growth of HeLa cells. Expression of E8∧E2C proteins rapidly increased the protein levels of the E6 and E7 targets p53 and p21, consistent with the repression of the endogenous HPV18 E6/E7 promoter. All E8∧E2C proteins induced G(1) arrest more efficiently than E2 proteins and activated senescence markers. Furthermore, we demonstrate that the 31E8 domain can be functionally replaced by the KRAB repression domain derived from KOX1. The KRAB-E2C fusion protein possesses long-distance transcriptional-repression activity and inhibits the growth of HeLa cells comparably to E8∧E2C. Taken together, our results suggest that the E8∧E2C proteins of HPV16, -18, and -31 are highly conserved transcriptional repressors that inhibit the growth of HeLa cells by repression of E6/E7 transcription but do not have proapoptotic activities.
authors.affiliation: University Hospital Tuebingen, Institute for Medical Virology and Epidemiology of Viral Diseases, Division of Experimental Virology, Elfriede-Aulhorn-Str. 6, 72076 Tuebingen, Germany.
authors.forename: Jasmin
authors.initials: J
authors.lastname: Fertey
authors.forename: José
authors.initials: J
authors.lastname: Hurst
authors.forename: Elke
authors.initials: E
authors.lastname: Straub
authors.forename: Astrid
authors.initials: A
authors.lastname: Schenker
authors.forename: Thomas
authors.initials: T
authors.lastname: Iftner
authors.forename: Frank
authors.initials: F
authors.lastname: Stubenrauch
mesh_terms: D049109:Cell Proliferation; D050759:Cyclin-Dependent Kinase Inhibitor p21 / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D004847:Epithelial Cells / Q000821:virology*; D015967:Gene Expression Regulation, Viral; D006367:HeLa Cells; D052162:Human papillomavirus 16 / Q000472:pathogenicity*; D052161:Human papillomavirus 18 / Q000472:pathogenicity*; D058952:Human papillomavirus 31 / Q000472:pathogenicity*; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000235:genetics / Q000378:metabolism*; D011401:Promoter Regions, Genetic; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism
chemical_list: C493956:CDKN1A protein, human; D050759:Cyclin-Dependent Kinase Inhibitor p21; D004268:DNA-Binding Proteins; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D016159:Tumor Suppressor Protein p53