Ubiquitin-dependent proteolysis of trihydrophobin 1 (TH1) by the human papilloma virus E6-associated protein (E6-AP).

Human Papilloma virus E6-associated protein (E6-AP), which is known as an E3 ubiquitin ligase, mediates ubiquitination and subsequent degradation of a series of cellular proteins. In this paper, we identify here trihydrophobin 1 (TH1), an integral subunit of the human negative transcription elongation factor (NELF) complex, as a novel E6-AP ...
interaction protein and a target of E6-AP-mediated degradation. Overexpression of E6-AP results in degradation of TH1 in a dose-dependent manner, whereas knock-down of endogenous E6-AP elevates the TH1 protein level. TH1 protein turnover is substantially faster, compared to controls, in cells that overexpressed E6-AP. Wild-type E6-AP promotes the ubiquitination of TH1, while a catalytically inactive point mutant of E6-AP abolishes its ubiquitination. Furthermore, in vitro ubiquitination assay also demonstrates that TH1 can be ubiquitinated by E6-AP. The degradation is blocked by treatment with proteasome inhibitor MG132. Herein, we provide strong evidence that TH1 is a specific substrate that is targeted for degradation through E6-AP-catalyzed polyubiquitination.
Mesh Terms:
Carcinoma, Hepatocellular, Carrier Proteins, Cell Line, Tumor, DNA, Complementary, Gene Expression Regulation, Enzymologic, Gene Library, Glutathione Transferase, Half-Life, Hela Cells, Human papillomavirus 6, Humans, Hydrolysis, Liver Neoplasms, Oncogene Proteins, Viral, Plasmids, Point Mutation, Protein Binding, Recombinant Proteins, Transfection, Two-Hybrid System Techniques, Ubiquitin-Protein Ligases, Ubiquitins
J. Cell. Biochem.
Date: May. 01, 2007
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