title: The high-risk human papillomavirus type 16 E6 counters the GAP function of E6TP1 toward small Rap G proteins.
abstract: We have recently identified E6TP1 (E6-targeted protein 1) as a novel high-risk human papillomavirus type 16 (HPV16) E6-binding protein. Importantly, mutational analysis of E6 revealed a strong correlation between the transforming activity and its abilities to bind and target E6TP1 for ubiquitin-mediated degradation. As a region within E6TP1 has high homology with GAP domains of known and putative Rap GTPase-activating proteins (GAPs), these results raised the possibility that HPV E6 may alter the Rap small-G-protein signaling pathway. Using two different approaches, we now demonstrate that human E6TP1 exhibits GAP activity for Rap1 and Rap2, confirming recent findings that a closely related rat homologue exhibits Rap-specific GAP activity. Using mutational analysis, we localize the GAP activity to residues 240 to 945 of E6TP1. Significantly, we demonstrate that coexpression of HPV16 E6, by promoting the degradation of E6TP1, enhances the GTP loading of Rap. These results support a role of Rap small-G-protein pathway in E6-mediated oncogenesis.
authors.affiliation: Division of Radiation and Cancer Biology, Department of Radiation Oncology, New England Medical Center, Boston, Massachusetts 02111, USA.
authors.forename: Latika
authors.initials: L
authors.lastname: Singh
authors.forename: Qingshen
authors.initials: Q
authors.lastname: Gao
authors.forename: Ajay
authors.initials: A
authors.lastname: Kumar
authors.forename: Takaya
authors.initials: T
authors.lastname: Gotoh
authors.forename: David E
authors.initials: DE
authors.lastname: Wazer
authors.forename: Hamid
authors.initials: H
authors.lastname: Band
authors.forename: Larry A
authors.initials: LA
authors.lastname: Feig
authors.forename: Vimla
authors.initials: V
authors.lastname: Band
mesh_terms: D002460:Cell Line; D020690:GTPase-Activating Proteins / Q000502:physiology*; D006801:Humans; D009856:Oncogene Proteins, Viral / Q000502:physiology*; D012097:Repressor Proteins; D020668:rap GTP-Binding Proteins / Q000502:physiology*
chemical_list: C068651:E6 protein, Human papillomavirus type 16; C116934:E6-target protein 1; D020690:GTPase-Activating Proteins; D009856:Oncogene Proteins, Viral; D012097:Repressor Proteins; D020668:rap GTP-Binding Proteins