The oncoprotein gankyrin binds to MDM2/HDM2, enhancing ubiquitylation and degradation of p53.

Gankyrin is an ankyrin repeat oncoprotein commonly overexpressed in hepatocellular carcinomas. Gankyrin interacts with the S6 proteasomal ATPase and accelerates the degradation of the tumor suppressor Rb. We show here that gankyrin has an antiapoptotic activity in cells exposed to DNA damaging agents. Downregulation of gankyrin induces apoptosis in cells with wild-type p53. In vitro and in vivo experiments revealed that gankyrin binds to Mdm2, facilitating p53-Mdm2 binding, and increases ubiquitylation and degradation of p53. Gankyrin also enhances Mdm2 autoubiquitylation in the absence of p53. Downregulation of gankyrin reduced amounts of Mdm2 and p53 associated with the 26S proteasome. Thus, gankyrin is a cofactor that increases the activities of Mdm2 on p53 and probably targets polyubiquitylated p53 into the 26S proteasome.

[1]  S. Jentsch,et al.  A Novel Ubiquitination Factor, E4, Is Involved in Multiubiquitin Chain Assembly , 1999, Cell.

[2]  D. Livingston,et al.  Polyubiquitination of p53 by a Ubiquitin Ligase Activity of p300 , 2003, Science.

[3]  Yusuke Nakamura,et al.  Genetic Changes and Histopathological Grades in Human Hepatocellular Carcinomas , 1993, Japanese journal of cancer research : Gann.

[4]  J. Fujita,et al.  A novel protein overexpressed in hepatoma accelerates export of NF-kappa B from the nucleus and inhibits p53-dependent apoptosis. , 2002, Cancer cell.

[5]  S. T. Kim,et al.  ATM-dependent phosphorylation of Mdm2 on serine 395: role in p53 activation by DNA damage. , 2001, Genes & development.

[6]  Katsuhiko Itoh,et al.  Reduced stability of retinoblastoma protein by gankyrin, an oncogenic ankyrin-repeat protein overexpressed in hepatomas , 2000, Nature Medicine.

[7]  R. Baker,et al.  Gankyrin Is an Ankyrin-repeat Oncoprotein That Interacts with CDK4 Kinase and the S6 ATPase of the 26 S Proteasome* , 2002, The Journal of Biological Chemistry.

[8]  Guillermina Lozano,et al.  Pirh2, a p53-Induced Ubiquitin-Protein Ligase, Promotes p53 Degradation , 2003, Cell.

[9]  J. Ericsson,et al.  YY1 inhibits the activation of the p53 tumor suppressor in response to genotoxic stress. , 2004, Proceedings of the National Academy of Sciences of the United States of America.

[10]  D. Lane,et al.  Mdm2-Mediated NEDD8 Conjugation of p53 Inhibits Its Transcriptional Activity , 2004, Cell.

[11]  Yili Yang,et al.  Regulating the p53 system through ubiquitination , 2004, Oncogene.

[12]  Yoshiharu Kawaguchi,et al.  MDM2–HDAC1‐mediated deacetylation of p53 is required for its degradation , 2002, The EMBO journal.

[13]  A. Ciechanover,et al.  Ubiquitin‐mediated proteolysis: biological regulation via destruction , 2000, BioEssays : news and reviews in molecular, cellular and developmental biology.

[14]  M. Tsai,et al.  Novel insights into the INK4-CDK4/6-Rb pathway: counter action of gankyrin against INK4 proteins regulates the CDK4-mediated phosphorylation of Rb. , 2002, Biochemistry.

[15]  Patrick Dowd,et al.  The ubiquitin ligase COP1 is a critical negative regulator of p53 , 2004, Nature.

[16]  M. Boyd,et al.  Regulation of p53 and MDM2 Activity by MTBP , 2005, Molecular and Cellular Biology.

[17]  D. Hanahan,et al.  The Hallmarks of Cancer , 2000, Cell.

[18]  P. Chène.  Inhibiting the p53–MDM2 interaction: an important target for cancer therapy , 2003, Nature Reviews Cancer.

[19]  Andreas Villunger,et al.  p53- and Drug-Induced Apoptotic Responses Mediated by BH3-Only Proteins Puma and Noxa , 2003, Science.

[20]  H. Kawai,et al.  Critical Contribution of the MDM2 Acidic Domain to p53 Ubiquitination , 2003, Molecular and Cellular Biology.

[21]  Wei Gu,et al.  Ubiquitination, phosphorylation and acetylation: the molecular basis for p53 regulation. , 2003, Current opinion in cell biology.

[22]  Xin Lu,et al.  Live or let die: the cell's response to p53 , 2002, Nature Reviews Cancer.

[23]  M. Horikoshi,et al.  Crystal Structure of the Homolog of the Oncoprotein Gankyrin, an Interactor of Rb and CDK4/6* , 2004, Journal of Biological Chemistry.

[24]  Petra de Graaf,et al.  Critical Role for a Central Part of Mdm2 in the Ubiquitylation of p53 , 2003, Molecular and Cellular Biology.

[25]  Scott W. Lowe,et al.  Apoptosis A Link between Cancer Genetics and Chemotherapy , 2002, Cell.

[26]  A. Ciechanover,et al.  Complete switch from Mdm2 to human papillomavirus E6-mediated degradation of p53 in cervical cancer cells. , 2001, Proceedings of the National Academy of Sciences of the United States of America.

[27]  R. Hay,et al.  Multiple C-Terminal Lysine Residues Target p53 for Ubiquitin-Proteasome-Mediated Degradation , 2000, Molecular and Cellular Biology.

[28]  Chaowei Wu,et al.  Regulation of cellular response to oncogenic and oxidative stress by Seladin-1 , 2004, Nature.

[29]  M. Oren,et al.  The p53-Mdm2 module and the ubiquitin system. , 2003, Seminars in cancer biology.

[30]  S. Grossman,et al.  Yin Yang 1 Is a Negative Regulator of p53 , 2004, Cell.

[31]  P. Raychaudhuri,et al.  Cul4A Physically Associates with MDM2 and Participates in the Proteolysis of p53 , 2004, Cancer Research.

[32]  A. Levine,et al.  Surfing the p53 network , 2000, Nature.

[33]  R. Copeland,et al.  Human mdm2 Mediates Multiple Mono-ubiquitination of p53 by a Mechanism Requiring Enzyme Isomerization* , 2001, The Journal of Biological Chemistry.

[34]  S. Lowe,et al.  Control of apoptosis by p53 , 2003, Oncogene.

[35]  A. Ashkenazi,et al.  Tumor Necrosis Factor An Apoptosis JuNKie? , 2004, Cell.

[36]  K. Nakayama,et al.  U Box Proteins as a New Family of Ubiquitin-Protein Ligases* , 2001, The Journal of Biological Chemistry.

[37]  S. Grossman,et al.  A post-ubiquitination role for MDM2 and hHR23A in the p53 degradation pathway , 2004, Oncogene.

[38]  T. Sakurai,et al.  MAGE-A4 Interacts with the Liver Oncoprotein Gankyrin and Suppresses Its Tumorigenic Activity* , 2003, Journal of Biological Chemistry.

[39]  Muyang Li,et al.  Mono- Versus Polyubiquitination: Differential Control of p53 Fate by Mdm2 , 2003, Science.

[40]  Petr Pancoska,et al.  p53 has a direct apoptogenic role at the mitochondria. , 2003, Molecular cell.

[41]  R. Kanamaru,et al.  Screening the p53 status of human cell lines using a yeast functional assay , 1997, Molecular carcinogenesis.

[42]  M. Kitagawa,et al.  Enhanced Mdm2 activity inhibits pRB function via ubiquitin‐dependent degradation , 2005, The EMBO journal.

[43]  Yun‐Sil Lee,et al.  Sequential changes in hepatocarcinogenesis induced by diethylnitrosamine plus thioacetamide in Fischer 344 rats: Induction of gankyrin expression in liver fibrosis, pRB degradation in cirrhosis, and methylation of p16INK4A exon 1 in hepatocellular carcinoma , 2001, Molecular carcinogenesis.

[44]  C. Finlay,et al.  The mdm-2 oncogene can overcome wild-type p53 suppression of transformed cell growth , 1993, Molecular and cellular biology.

[45]  D. Lane,et al.  Different effects of p14ARF on the levels of ubiquitinated p53 and Mdm2 in vivo , 2001, Oncogene.

[46]  R. Hartmann-Petersen,et al.  Transferring substrates to the 26S proteasome. , 2003, Trends in biochemical sciences.

[47]  C. Pickart,et al.  Mechanisms underlying ubiquitination. , 2001, Annual review of biochemistry.

[48]  S. Krzywda,et al.  The Crystal Structure of Gankyrin, an Oncoprotein Found in Complexes with Cyclin-dependent Kinase 4, a 19 S Proteasomal ATPase Regulator, and the Tumor Suppressors Rb and p53* , 2004, Journal of Biological Chemistry.