Journal article

Ubiquitin ligase E6AP mediates nonproteolytic polyubiquitylation of beta-catenin independent of the E6 oncoprotein

Yael Kuslansky, Sophia Sominsky, Anna Jackman, Cristina Gamell, Brendon J Monahan, Ygal Haupt, Rina Rosin-Arbesfeld, Levana Sherman



Recently, we showed that the ubiquitin ligase E6AP stabilizes β-catenin and activates its transcriptional activity. These activities were enhanced by the human papillomavirus (HPV) E6 protein. In the present study, we explored the function of E6AP, which increases β-catenin stabilization and transcriptional activation. Here, we report that E6AP interacts with β-catenin and mediates its nonproteolytic ubiquitylation, as evidenced in transiently transfected cell-based and in vitro reconstitution ubiquitylation assays. Overexpression of E6AP increased β-catenin polyubiquitylation and, consistent with that, knockdown or knock-out of E6AP expression reduced β-catenin polyubiquitylation. The ubiqu..

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Awarded by Israel Science Foundation, Israel

Awarded by NMHRC

Funding Acknowledgements

We are grateful to Dr Martin Scheffner (Department of Biology, University of Konstanz, Konstanz, Germany) for kindly providing the expression plasmid for E6AP; Dr Arnona Gazit and Dr Abraham Yaniv (Tel Aviv University, Tel Aviv, Israel) for kindly providing the Wnt3a, HFz1, beta-catenin and TCF4-HA expression plasmids; Dr Randall T. Moon (Howard Hughes Medical Institute, University of washington School of Medicine, Seattle, WA, USA) for kindly providing the superTOPFLASH and superFOPFLASH plasmids; Dr C. Albanese (Georgetown University Medical Center, Washington DC, USA) for kindly providing the cyclin D1 reporter plasmid; Dr Dirk Bohmann (Rochester University, Rochester, NY, USA) for kindly providing the HA-ubiquitin expression plasmid; Dr David Pim (International Centre for Genetic Engineering and Biotechnology, Trieste, Italy) for kindly providing the HPV16 E7-HA expression plasmid; Dr Denise Galloway (Fred Hutchinson Cancer Research Center, UW Medicine, Seattle, WA, USA) for kindly providing the shE6AP expression plasmid; and Dr Gerardo Lederkremer (Tel-Aviv University, Tel-Aviv, Israel) for kindly providing the pMH-ManIc1-HA plasmid. This work was supported by grant no. 1253-10 from the Israel Science Foundation, Israel, awarded to L. S., and in part by NMHRC project grants to Y. H. (1026988, 1049179, 1063389), an NHMRC Fellowship to Y. H. (9628426), and a VCA Prat Foundation Fellowship to C. F. G. This work was done in partial fulfilment of the requirements for the PhD degrees of Y. K. and S. S., Sackler Faculty of Medicine, Tel-Aviv University, Israel.