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UBE4B promotes Hdm2-mediated degradation of the tumor suppressor p53

Nature Medicine volume 17, pages 347355 (2011) | Download Citation

Abstract

The TP53 gene (encoding the p53 tumor suppressor) is rarely mutated, although frequently inactivated, in medulloblastoma and ependymoma. Recent work in mouse models showed that the loss of p53 accelerated the development of medulloblastoma. The mechanism underlying p53 inactivation in human brain tumors is not completely understood. We show that ubiquitination factor E4B (UBE4B), an E3 and E4 ubiquitin ligase, physically interacts with p53 and Hdm2 (also known as Mdm2 in mice). UBE4B promotes p53 polyubiquitination and degradation and inhibits p53-dependent transactivation and apoptosis. Notably, silencing UBE4B expression impairs xenotransplanted tumor growth in a p53-dependent manner and overexpression of UBE4B correlates with decreased expression of p53 in these tumors. We also show that UBE4B overexpression is often associated with amplification of its gene in human brain tumors. Our data indicate that amplification and overexpression of UBE4B represent previously undescribed molecular mechanisms of inactivation of p53 in brain tumors.

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Acknowledgements

We gratefully acknowledge W. Gu (Columbia University) for the His-ubiquitin (wild-type) and His-Ub-ko plasmids, A.G. Jochemsen (Erasmus University Medical Center) for the Myc-Mdm2 plasmid, C. Blattner (Universität Heidelberg) for pSuper.neo.gpf-Mdm2 siRNA plasmid, J.A. Mahoney (Johns Hopkins University) for pEF-DEST51-Flag-UBE4B plasmid, B. Vogelstein (Johns Hopkins University) for HCT116 TP53−/− cells, S. Benchimol (York University) for BJT and BJT/DD cell lines and G. Lozano (University of Texas, M.D. Anderson Cancer Center) for Mdm2−/− Trp53−/− MEFs as described in the text. We thank T. Turner for technical help in making the figures. This work was supported by grants from the Alberta Heritage Foundation for Medical Research and Canadian Institutes of Health Research (to R.P.L.) and from the US National Institutes of Health (to S.L.P.). R.P.L. is an Alberta Heritage Foundation for Medical Research scholar.

Author information

Affiliations

  1. Heritage Medical Research Center, Department of Laboratory Medicine and Pathology, University of Alberta, Edmonton, Alberta, Canada.

    • Hong Wu
    •  & Roger P Leng
  2. Department of Neurology, Children's Hospital Boston, Harvard Medical School, Boston, Massachusetts, USA.

    • Scott L Pomeroy
    • , Natalia Teider
    •  & Juliana Mariani
  3. Department of Neurosurgery, Massachusetts General Hospital, Harvard Medical School, Boston, Massachusetts, USA.

    • Manuel Ferreira
  4. Department of Molecular and Cellular Biology, Medical Institute of Bioregulation, Kyushu University, Higashi-ku, Fukuoka, Japan.

    • Keiichi I Nakayama
  5. Department of Molecular Biochemistry, Hokkaido University Graduate School of Medicine, Kita-ku, Sapporo, Japan.

    • Shigetsugu Hatakeyama
  6. Department of Pathology and Molecular Medicine, Queen's University, Kingston, Ontario, Canada.

    • Victor A Tron
  7. Department of Biochemistry, University of Alberta, Edmonton, Alberta, Canada.

    • Linda F Saltibus
    •  & Leo Spyracopoulos

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Contributions

H.W. and R.P.L. contributed to study design, performed most of the experiments, analyzed and interpreted the data and wrote the manuscript. S.L.P. provided logistical support and all tumor samples and interpreted and discussed the data. M.F. provided technical support and experimental assistance. N.T. conducted the western blotting for the pediatric astrocytoma tissues, isolated genomic DNAs from various tumor samples, carried out mutation detection for p53 in various tumor tissues and medulloblastoma cell lines and did long-term colony assays. J.M. collected tissue samples from various types of human brain tumors, cared for Ptch+/− mice, conducted all the mouse genotyping and isolated the cerebellum and cortex from the Ptch+/− mice. K.I.N. and S.H. provided the study material and technical support. V.A.T. provided technical support. L.F.S. conducted the FPLC protein purification experiments. L.S. provided technical support for the gel filtration. R.P.L. supervised and directed the project.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to Roger P Leng.

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    Supplementary Text and Figures

    Supplementary Figures 1–8, Supplementary Table 1 and Supplementary Methods

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DOI

https://doi.org/10.1038/nm.2283

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