title: E3 ligase EDD1/UBR5 is utilized by the HPV E6 oncogene to destabilize tumor suppressor TIP60.
abstract: Tat-interacting protein of 60 kDa (TIP60) is an essential lysine acetyltransferase implicated in transcription, DNA damage response and apoptosis. TIP60 protein expression is reduced in cancers. In cervical cancers, human papillomavirus (HPV) E6 oncogene targets cellular p53, Bak and some of the PDZ domain-containing proteins for proteasome-mediated degradation through E6AP ligase. Recently, E6 oncogene from high-risk and low-risk categories was also shown to target TIP60. However, the molecular mechanisms and whether destabilization of TIP60 contributes to HPV E6-mediated transformation remain unanswered. Our proteomic analyses revealed EDD1 (E3 identified by differential display), an E3 ligase generally overexpressed in cancers as a novel interacting partner of TIP60. By investigating protein turnover and ubiquitination assays, we show that EDD1 negatively regulates TIP60's stability through the proteasome pathway. Strikingly, HPV E6 uses this function of EDD1 to destabilize TIP60. Colony-formation assays and soft agar assays show that gain of function of TIP60 or depletion of EDD1 in HPV-positive cervical cancer cells significantly inhibits cell growth in vitro. This phenotype is strongly supported by the in-vivo studies where re-activation of TIP60 in cervical cancer cells dramatically reduces tumor formation. In summary, we have discovered a novel ligase through which E6 destabilizes TIP60. Currently, in the absence of an effective therapeutic vaccine for malignant cervical cancers, cervical cancer still remains to be a major disease burden. Hence, our studies implying a distinct tumor suppressor role for TIP60 in cervical cancers show that reactivation of TIP60 could be of therapeutic value.
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.
authors.forename: V K
authors.initials: VK
authors.lastname: Subbaiah
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.
authors.forename: Y
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.|Department of Biochemistry, National University of Singapore, Singapore.
authors.forename: D
authors.initials: D
authors.lastname: Rajagopalan
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.
authors.forename: L N
authors.initials: LN
authors.lastname: Abdullah
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.|NUS Graduate School for Integrative Sciences and Engineering, National University of Singapore, Singapore.
authors.forename: N S L
authors.initials: NS
authors.lastname: Yeo-Teh
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: V
authors.initials: V
authors.lastname: Tomaić
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: L
authors.initials: L
authors.lastname: Banks
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Trieste, Italy.
authors.forename: M P
authors.initials: MP
authors.lastname: Myers
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.|Department of Pharmacology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.
authors.forename: E K
authors.initials: EK
authors.lastname: Chow
authors.affiliation: Cancer Science Institute of Singapore, National University of Singapore, Singapore.|Department of Biochemistry, National University of Singapore, Singapore.
authors.forename: S
authors.initials: S
authors.lastname: Jha
mesh_terms: D002455:Cell Division / Q000235:genetics; D002460:Cell Line; D016147:Genes, Tumor Suppressor; D051548:Histone Acetyltransferases / Q000378:metabolism*; D006801:Humans; D000074443:Lysine Acetyltransferase 5; D009856:Oncogene Proteins, Viral / Q000235:genetics*; D009857:Oncogenes; D027383:Papillomaviridae / Q000235:genetics*; D011485:Protein Binding; D040901:Proteomics; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D009856:Oncogene Proteins, Viral; D051548:Histone Acetyltransferases; C098489:KAT5 protein, human; D000074443:Lysine Acetyltransferase 5; C117617:UBR5 protein, human; D044767:Ubiquitin-Protein Ligases