title: Role of ubiquitin and the HPV E6 oncoprotein in E6AP-mediated ubiquitination.
abstract: Deregulation of the ubiquitin ligase E6 associated protein (E6AP) encoded by the UBE3A gene has been associated with three different clinical pictures. Hijacking of E6AP by the E6 oncoprotein of distinct human papillomaviruses (HPV) contributes to the development of cervical cancer, whereas loss of E6AP expression or function is the cause of Angelman syndrome, a neurodevelopmental disorder, and increased expression of E6AP has been involved in autism spectrum disorders. Although these observations indicate that the activity of E6AP has to be tightly controlled, only little is known about how E6AP is regulated at the posttranslational level. Here, we provide evidence that the hydrophobic patch of ubiquitin comprising Leu-8 and Ile-44 is important for E6AP-mediated ubiquitination, whereas it does not affect the catalytic properties of the isolated catalytic HECT domain of E6AP. Furthermore, we show that the HPV E6 oncoprotein rescues the disability of full-length E6AP to use a respective hydrophobic patch mutant of ubiquitin for ubiquitination and that it stimulates E6AP-mediated ubiquitination of Ring1B, a known substrate of E6AP, in vitro and in cells. Based on these data, we propose that E6AP exists in at least two different states, an active and a less active or latent one, and that the activity of E6AP is controlled by noncovalent interactions with ubiquitin and allosteric activators such as the HPV E6 oncoprotein.
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany; Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany;
authors.forename: Franziska
authors.initials: F
authors.lastname: Mortensen
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany; Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Daniel
authors.initials: D
authors.lastname: Schneider
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany;
authors.forename: Tanja
authors.initials: T
authors.lastname: Barbic
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany;
authors.forename: Anna
authors.initials: A
authors.lastname: Sladewska-Marquardt
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany;
authors.forename: Simone
authors.initials: S
authors.lastname: Kühnle
authors.affiliation: Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany; Department of Chemistry, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Marx
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany; Konstanz Research School Chemical Biology, University of Konstanz, 78457 Konstanz, Germany; martin.scheffner@uni-konstanz.de.
authors.forename: Martin
authors.initials: M
authors.lastname: Scheffner
mesh_terms: D000494:Allosteric Regulation; D000595:Amino Acid Sequence; D055162:Biocatalysis; D045744:Cell Line, Tumor; D003545:Cysteine / Q000378:metabolism; D006801:Humans; D057927:Hydrophobic and Hydrophilic Interactions; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D025801:Ubiquitin / Q000737:chemistry / Q000378:metabolism*; D044763:Ubiquitin-Conjugating Enzymes / Q000737:chemistry / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D054875:Ubiquitination
chemical_list: D010455:Peptides; D025801:Ubiquitin; C097309:UBE2D2 protein, human; C079437:UBE2L3 protein, human; D044763:Ubiquitin-Conjugating Enzymes; C471639:UBE3A protein, human; D044767:Ubiquitin-Protein Ligases; D003545:Cysteine
keywords: Angelman syndrome; E6 oncoprotein; E6AP/UBE3A; human papillomavirus; ubiquitin