[UBE3A_HUMAN] Defects in UBE3A are a cause of Angelman syndrome (AS) [MIM:105830]; also known as 'happy puppet syndrome'. AS is characterized by features of severe motor and intellectual retardation, microcephaly, ataxia, frequent jerky limb movements and flapping of the arms and hands, hypotonia, hyperactivity, hypopigmentation, seizures, absence of speech, frequent smiling and episodes of paroxysmal laughter, and an unusual facies characterized by macrostomia, a large mandible and open-mouthed expression, a great propensity for protruding the tongue ('tongue thrusting'), and an occipital groove.
[UBE3A_HUMAN] E3 ubiquitin-protein ligase which accepts ubiquitin from an E2 ubiquitin-conjugating enzyme in the form of a thioester and transfers it to its substrates. Several substrates have been identified including the RAD23A and RAD23B, MCM7 (which is involved in DNA replication), annexin A1, the PML tumor suppressor, and the cell cycle regulator CDKN1B. Catalyzes the high-risk human papilloma virus E6-mediated ubiquitination of p53/TP53, contributing to the neoplastic progression of cells infected by these viruses. Additionally, may function as a cellular quality control ubiquitin ligase by helping the degradation of the cytoplasmic misfolded proteins. Finally, UBE3A also promotes its own degradation in vivo.
The E6AP ubiquitin-protein ligase (E3) mediates the human papillomavirus-induced degradation of the p53 tumor suppressor in cervical cancer and is mutated in Angelman syndrome, a neurological disorder. The crystal structure of the catalytic hect domain of E6AP reveals a bilobal structure with a broad catalytic cleft at the junction of the two lobes. The cleft consists of conserved residues whose mutation interferes with ubiquitin-thioester bond formation and is the site of Angelman syndrome mutations. The crystal structure of the E6AP hect domain bound to the UbcH7 ubiquitin-conjugating enzyme (E2) reveals the determinants of E2-E3 specificity and provides insights into the transfer of ubiquitin from the E2 to the E3.
Structure of an E6AP-UbcH7 complex: insights into ubiquitination by the E2-E3 enzyme cascade.,Huang L, Kinnucan E, Wang G, Beaudenon S, Howley PM, Huibregtse JM, Pavletich NP Science. 1999 Nov 12;286(5443):1321-6. PMID:10558980
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
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↑ Mishra A, Godavarthi SK, Maheshwari M, Goswami A, Jana NR. The ubiquitin ligase E6-AP is induced and recruited to aggresomes in response to proteasome inhibition and may be involved in the ubiquitination of Hsp70-bound misfolded proteins. J Biol Chem. 2009 Apr 17;284(16):10537-45. Epub 2009 Feb 20. PMID:19233847 doi:M806804200
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↑ Martinez-Noel G, Galligan JT, Sowa ME, Arndt V, Overton TM, Harper JW, Howley PM. Identification and proteomic analysis of distinct UBE3A/E6AP protein complexes. Mol Cell Biol. 2012 Aug;32(15):3095-106. doi: 10.1128/MCB.00201-12. Epub 2012 May, 29. PMID:22645313 doi:10.1128/MCB.00201-12
↑ Huang L, Kinnucan E, Wang G, Beaudenon S, Howley PM, Huibregtse JM, Pavletich NP. Structure of an E6AP-UbcH7 complex: insights into ubiquitination by the E2-E3 enzyme cascade. Science. 1999 Nov 12;286(5443):1321-6. PMID:10558980