World Library  
Flag as Inappropriate
Email this Article


Article Id: WHEBN0003731311
Reproduction Date:

Title: Mdm2  
Author: World Heritage Encyclopedia
Language: English
Subject: P14arf, SWI/SNF, Ubiquitin ligase, Karen Vousden, P16
Collection: Human Proteins, Oncogenes, Proteins
Publisher: World Heritage Encyclopedia


MDM2 proto-oncogene, E3 ubiquitin protein ligase
Solution structure of Mdm2. [1]
Available structures
PDB Ortholog search: PDBe, RCSB
Symbols  ; ACTFS; HDMX; hdm2
External IDs ChEMBL: GeneCards:
RNA expression pattern
Species Human Mouse
RefSeq (mRNA)
RefSeq (protein)
Location (UCSC)
PubMed search

Mouse double minute 2 homolog (MDM2) also known as E3 ubiquitin-protein ligase Mdm2 is a protein that in humans is encoded by the MDM2 gene.[2][3] Mdm2 is an important negative regulator of the p53 tumor suppressor. Mdm2 protein functions both as an E3 ubiquitin ligase that recognizes the N-terminal trans-activation domain (TAD) of the p53 tumor suppressor and an inhibitor of p53 transcriptional activation.


  • Discovery and expression in tumor cells 1
  • Ubiquitination target: p53 2
  • E3 ligase activity 3
  • Structure and function 4
  • Regulation 5
  • Interactions 6
  • Mdm2 p53-independent role 7
  • References 8
  • Further reading 9
  • External links 10

Discovery and expression in tumor cells

The murine double minute (mdm2) oncogene, which codes for the Mdm2 protein, was originally cloned, along with two other genes (mdm1 and mdm3) from the transformed mouse cell line 3T3-DM. Mdm2 overexpression, in cooperation with oncogenic Ras, promotes transformation of primary rodent fibroblasts, and mdm2 expression led to tumor formation in nude mice. The human homologue of this protein was later identified and is sometimes called Hdm2. Further supporting the role of mdm2 as an oncogene, several human tumor types have been shown to have increased levels of Mdm2, including soft tissue sarcomas and osteosarcomas as well as breast tumors. An additional Mdm2 family member, Mdm4 (also called MdmX), has been discovered and is also an important negative regulator of p53.

Ubiquitination target: p53

The key target of Mdm2 is the p53 tumor suppressor. Mdm2 has been identified as a p53 interacting protein that represses p53 transcriptional activity. Mdm2 achieves this repression by binding to and blocking the N-terminal trans-activation domain of p53. Mdm2 is a p53 responsive gene—that is, its transcription can be activated by p53. Thus when p53 is stabilized, the transcription of Mdm2 is also induced, resulting in higher Mdm2 protein levels.

E3 ligase activity

Mdm2 also acts as an E3 ubiquitin ligase, targeting both itself and p53 for degradation by the proteasome (see also ubiquitin). Several lysine residues in p53 C-terminus have been identified as the sites of ubiquitination, and it has been shown that p53 protein levels are downregulated by Mdm2 in a proteasome-dependent manner. Mdm2 is capable of auto-polyubiquitination, and in complex with p300, a cooperating E3 ubiquitin ligase, is capable of polyubiquitinating p53. In this manner, Mdm2 and p53 are the members of a negative feedback control loop that keeps the level of p53 low in the absence of p53-stabilizing signals. This loop can be interfered with by kinases and genes like p14arf when p53 activation signals, including DNA damage, are high.

Structure and function

The full-length transcript of the mdm2 gene encodes a protein of 491 amino acids with a predicted molecular weight of 56kDa. This protein contains several conserved structural domains including an N-terminal p53 interaction domain, the structure of which has been solved using x-ray crystallography. The Mdm2 protein also contains a central acidic domain (residues 230-300). The phosphorylation of residues within this domain appears to be important for regulation of Mdm2 function. In addition, this region contains nuclear export and import signals that are essential for proper nuclear-cytoplasmic trafficking of Mdm2. Another conserved domain within the Mdm2 protein is a zinc finger domain, the function of which is poorly understood.

Mdm2 also contains a C-terminal RING domain (amino acid resdiues 430-480), which contains a Cis3-His2-Cis3 consensus that coordinates two molecules of zinc. These residues are required for zinc binding, which is essential for proper folding of the RING domain. The RING domain of Mdm2 confers E3 ubiquitin ligase activity and is sufficient for E3 ligase activity in Mdm2 RING autoubiquitination. The RING domain of Mdm2 is unique in that it incorporates a conserved Walker A or P-loop motif characteristic of nucleotide binding proteins, as well as a nucleolar localization sequence. The RING domain also binds specifically to RNA, although the function of this is poorly understood.


There are several known mechanisms for regulation of Mdm2. One of these mechanisms is phosphorylation of the Mdm2 protein. Mdm2 is phosphorylated at multiple sites in cells. Following DNA damage, phosphorylation of Mdm2 leads to changes in protein function and stabilization of p53. Additionally, phosphorylation at certain residues within the central acidic domain of Mdm2 may stimulate its ability to target p53 for degradation. The induction of the p14arf protein, the alternate reading frame product of the p16INK4a locus, is also a mechanism of negatively regulating the p53-Mdm2 interaction. p14arf directly interacts with Mdm2 and leads to up-regulation of p53 transcriptional response. ARF sequesters Mdm2 in the nucleolus, resulting in inhibition of nuclear export and activation of p53, since nuclear export is essential for proper p53 degradation.

Inhibitors of the MDM2-p53 interaction include the cis-imidazoline analog nutlin.[4]

Levels and stability of Mdm2 are also modulated by ubiquitylation. Mdm2 auto ubiquitylates itself, which allows for its degradation by the proteasome. Mdm2 also interacts with a ubiquitin specific protease, USP7, which can reverse Mdm2-ubiquitylation and prevent it from being degraded by the proteasome. It is interesting to note that USP7 also protects from degradation the p53 protein, which is a major target of Mdm2. Thus Mdm2 and USP7 form an intricate circuit to finely regulate the stability and activity of p53, whose levels are critical for its function.


Overview of signal transduction pathways involved in apoptosis.

Mdm2 has been shown to interact with:

Mdm2 p53-independent role

Mdm2 overexpression was shown to inhibit DNA double-strand break repair mediated through a novel, direct interaction between Mdm2 and Nbs1 and independent of p53. Regardless of p53 status, increased levels of Mdm2, but not Mdm2 lacking its Nbs1-binding domain, caused delays in DNA break repair, chromosomal abnormalities, and genome instability. These data demonstrated Mdm2-induced genome instability can be mediated through Mdm2:Nbs1 interactions and independent from its association with p53.


  1. ^ Uhrinova S, Uhrin D, Powers H, et al. (2005). "Structure of free MDM2 N-terminal domain reveals conformational adjustments that accompany p53-binding". J. Mol. Biol. 350 (3): 587–98.  
  2. ^ Oliner JD, Kinzler KW, Meltzer PS, George DL, Vogelstein B (July 1992). "Amplification of a gene encoding a p53-associated protein in human sarcomas". Nature 358 (6381): 80–3.  
  3. ^ Wade M, Wong ET, Tang M, Stommel JM, Wahl GM (November 2006). "Hdmx modulates the outcome of p53 activation in human tumor cells". J. Biol. Chem. 281 (44): 33036–44.  
  4. ^ Vassilev LT, Vu BT, Graves B, Carvajal D, Podlaski F, Filipovic Z, Kong N, Kammlott U, Lukacs C, Klein C, Fotouhi N, Liu EA (2004). "In vivo activation of the p53 pathway by small-molecule antagonists of MDM2". Science 303 (5659): 844–848.  
  5. ^ Goldberg Z, Vogt Sionov R, Berger M, Zwang Y, Perets R, Van Etten RA, Oren M, Taya Y, Haupt Y (July 2002). "Tyrosine phosphorylation of Mdm2 by c-Abl: implications for p53 regulation". EMBO J. 21 (14): 3715–27.  
  6. ^ a b Wang P, Wu Y, Ge X, Ma L, Pei G (March 2003). "Subcellular localization of beta-arrestins is determined by their intact N domain and the nuclear export signal at the C terminus". J. Biol. Chem. 278 (13): 11648–53.  
  7. ^ a b Shenoy SK, Xiao K, Venkataramanan V, Snyder PM, Freedman NJ, Weissman AM (August 2008). "Nedd4 mediates agonist-dependent ubiquitination, lysosomal targeting, and degradation of the beta2-adrenergic receptor". J. Biol. Chem. 283 (32): 22166–76.  
  8. ^ Wang P, Gao H, Ni Y, Wang B, Wu Y, Ji L, Qin L, Ma L, Pei G (February 2003). "Beta-arrestin 2 functions as a G-protein-coupled receptor-activated regulator of oncoprotein Mdm2". J. Biol. Chem. 278 (8): 6363–70.  
  9. ^ Zhao L, Samuels T, Winckler S, Korgaonkar C, Tompkins V, Horne MC, Quelle DE (January 2003). "Cyclin G1 has growth inhibitory activity linked to the ARF-Mdm2-p53 and pRb tumor suppressor pathways". Mol. Cancer Res. 1 (3): 195–206.  
  10. ^ a b Mirnezami AH, Campbell SJ, Darley M, Primrose JN, Johnson PW, Blaydes JP (July 2003). "Hdm2 recruits a hypoxia-sensitive corepressor to negatively regulate p53-dependent transcription". Curr. Biol. 13 (14): 1234–9.  
  11. ^ a b c Ivanchuk SM, Mondal S, Rutka JT (June 2008). "p14ARF interacts with DAXX: effects on HDM2 and p53". Cell Cycle 7 (12): 1836–50.  
  12. ^ Maguire M, Nield PC, Devling T, Jenkins RE, Park BK, Polański R, Vlatković N, Boyd MT (May 2008). "MDM2 regulates dihydrofolate reductase activity through monoubiquitination". Cancer Res. 68 (9): 3232–42.  
  13. ^ Grossman SR, Perez M, Kung AL, Joseph M, Mansur C, Xiao ZX, Kumar S, Howley PM, Livingston DM (October 1998). "p300/MDM2 complexes participate in MDM2-mediated p53 degradation". Mol. Cell 2 (4): 405–15.  
  14. ^ Miyamoto-Sato E, Fujimori S, Ishizaka M, Hirai N, Masuoka K, Saito R, Ozawa Y, Hino K, Washio T, Tomita M, Yamashita T, Oshikubo T, Akasaka H, Sugiyama J, Matsumoto Y, Yanagawa H (Feb 2010). "A comprehensive resource of interacting protein regions for refining human transcription factor networks". PloS One 5 (2).  
  15. ^ Ochocka AM, Kampanis P, Nicol S, Allende-Vega N, Cox M, Marcar L, Milne D, Fuller-Pace F, Meek D (February 2009). "FKBP25, a novel regulator of the p53 pathway, induces the degradation of MDM2 and activation of p53". FEBS Lett. 583 (4): 621–6.  
  16. ^ Brenkman AB, de Keizer PL, van den Broek NJ, Jochemsen AG, Burgering BM (2008). "Mdm2 induces mono-ubiquitination of FOXO4". PLoS ONE 3 (7): e2819.  
  17. ^ a b c Dai MS, Sun XX, Lu H (July 2008). "Aberrant expression of nucleostemin activates p53 and induces cell cycle arrest via inhibition of MDM2". Mol. Cell. Biol. 28 (13): 4365–76.  
  18. ^ Ito A, Kawaguchi Y, Lai CH, Kovacs JJ, Higashimoto Y, Appella E, Yao TP (November 2002). "MDM2-HDAC1-mediated deacetylation of p53 is required for its degradation". EMBO J. 21 (22): 6236–45.  
  19. ^ Chen D, Li M, Luo J, Gu W (April 2003). "Direct interactions between HIF-1 alpha and Mdm2 modulate p53 function". J. Biol. Chem. 278 (16): 13595–8.  
  20. ^ Ravi R, Mookerjee B, Bhujwalla ZM, Sutter CH, Artemov D, Zeng Q, Dillehay LE, Madan A, Semenza GL, Bedi A (January 2000). "Regulation of tumor angiogenesis by p53-induced degradation of hypoxia-inducible factor 1alpha". Genes Dev. 14 (1): 34–44.  
  21. ^ Legube G, Linares LK, Lemercier C, Scheffner M, Khochbin S, Trouche D (April 2002). "Tip60 is targeted to proteasome-mediated degradation by Mdm2 and accumulates after UV irradiation". EMBO J. 21 (7): 1704–12.  
  22. ^ Sehat B, Andersson S, Girnita L, Larsson O (July 2008). "Identification of c-Cbl as a new ligase for insulin-like growth factor-I receptor with distinct roles from Mdm2 in receptor ubiquitination and endocytosis". Cancer Res. 68 (14): 5669–77.  
  23. ^ Kadakia M, Brown TL, McGorry MM, Berberich SJ (December 2002). "MdmX inhibits Smad transactivation". Oncogene 21 (57): 8776–85.  
  24. ^ Tanimura S, Ohtsuka S, Mitsui K, Shirouzu K, Yoshimura A, Ohtsubo M (March 1999). "MDM2 interacts with MDMX through their RING finger domains". FEBS Lett. 447 (1): 5–9.  
  25. ^ Badciong JC, Haas AL (December 2002). "MdmX is a RING finger ubiquitin ligase capable of synergistically enhancing Mdm2 ubiquitination". J. Biol. Chem. 277 (51): 49668–75.  
  26. ^ Linke K, Mace PD, Smith CA, Vaux DL, Silke J, Day CL (May 2008). "Structure of the MDM2/MDMX RING domain heterodimer reveals dimerization is required for their ubiquitylation in trans". Cell Death Differ. 15 (5): 841–8.  
  27. ^ Yogosawa S, Miyauchi Y, Honda R, Tanaka H, Yasuda H (March 2003). "Mammalian Numb is a target protein of Mdm2, ubiquitin ligase". Biochem. Biophys. Res. Commun. 302 (4): 869–72.  
  28. ^ Colaluca IN, Tosoni D, Nuciforo P, Senic-Matuglia F, Galimberti V, Viale G, Pece S, Di Fiore PP (January 2008). "NUMB controls p53 tumour suppressor activity". Nature 451 (7174): 76–80.  
  29. ^ a b c Zhang Y, Wolf GW, Bhat K, Jin A, Allio T, Burkhart WA, Xiong Y (December 2003). "Ribosomal protein L11 negatively regulates oncoprotein MDM2 and mediates a p53-dependent ribosomal-stress checkpoint pathway". Mol. Cell. Biol. 23 (23): 8902–12.  
  30. ^ Zhang Y, Xiong Y, Yarbrough WG (March 1998). "ARF promotes MDM2 degradation and stabilizes p53: ARF-INK4a locus deletion impairs both the Rb and p53 tumor suppression pathways". Cell 92 (6): 725–34.  
  31. ^ Clark PA, Llanos S, Peters G (July 2002). "Multiple interacting domains contribute to p14ARF mediated inhibition of MDM2". Oncogene 21 (29): 4498–507.  
  32. ^ Pomerantz J, Schreiber-Agus N, Liégeois NJ, Silverman A, Alland L, Chin L, Potes J, Chen K, Orlow I, Lee HW, Cordon-Cardo C, DePinho RA (March 1998). "The Ink4a tumor suppressor gene product, p19Arf, interacts with MDM2 and neutralizes MDM2's inhibition of p53". Cell 92 (6): 713–23.  
  33. ^ Haupt Y, Maya R, Kazaz A, Oren M (May 1997). "Mdm2 promotes the rapid degradation of p53". Nature 387 (6630): 296–9.  
  34. ^ Honda R, Tanaka H, Yasuda H (December 1997). "Oncoprotein MDM2 is a ubiquitin ligase E3 for tumor suppressor p53". FEBS Lett. 420 (1): 25–7.  
  35. ^ Bálint E, Bates S, Vousden KH (July 1999). "Mdm2 binds p73 alpha without targeting degradation". Oncogene 18 (27): 3923–9.  
  36. ^ Zeng X, Chen L, Jost CA, Maya R, Keller D, Wang X, Kaelin WG, Oren M, Chen J, Lu H (May 1999). "MDM2 suppresses p73 function without promoting p73 degradation". Mol. Cell. Biol. 19 (5): 3257–66.  
  37. ^ Jin Y, Zeng SX, Dai MS, Yang XJ, Lu H (August 2002). "MDM2 inhibits PCAF (p300/CREB-binding protein-associated factor)-mediated p53 acetylation". J. Biol. Chem. 277 (34): 30838–43.  
  38. ^ Qiu W, Wu J, Walsh EM, Zhang Y, Chen CY, Fujita J, Xiao ZX (July 2008). "Retinoblastoma protein modulates gankyrin-MDM2 in regulation of p53 stability and chemosensitivity in cancer cells". Oncogene 27 (29): 4034–43.  
  39. ^ Zhang Z, Zhang R (March 2008). "Proteasome activator PA28 gamma regulates p53 by enhancing its MDM2-mediated degradation". EMBO J. 27 (6): 852–64.  
  40. ^ Marechal V, Elenbaas B, Piette J, Nicolas JC, Levine AJ (November 1994). "The ribosomal L5 protein is associated with mdm-2 and mdm-2-p53 complexes". Mol. Cell. Biol. 14 (11): 7414–20.  
  41. ^ Bernardi R, Scaglioni PP, Bergmann S, Horn HF, Vousden KH, Pandolfi PP (July 2004). "PML regulates p53 stability by sequestering Mdm2 to the nucleolus". Nat. Cell Biol. 6 (7): 665–72.  
  42. ^ Zhu H, Wu L, Maki CG (December 2003). "MDM2 and promyelocytic leukemia antagonize each other through their direct interaction with p53". J. Biol. Chem. 278 (49): 49286–92.  
  43. ^ Kurki S, Latonen L, Laiho M (October 2003). "Cellular stress and DNA damage invoke temporally distinct Mdm2, p53 and PML complexes and damage-specific nuclear relocalization". J. Cell. Sci. 116 (Pt 19): 3917–25.  
  44. ^ Wei X, Yu ZK, Ramalingam A, Grossman SR, Yu JH, Bloch DB, Maki CG (August 2003). "Physical and functional interactions between PML and MDM2". J. Biol. Chem. 278 (31): 29288–97.  
  45. ^ Ofir-Rosenfeld Y, Boggs K, Michael D, Kastan MB, Oren M (October 2008). "Mdm2 regulates p53 mRNA translation through inhibitory interactions with ribosomal protein L26". Mol. Cell 32 (2): 180–9.  
  46. ^ Chang L, Zhou B, Hu S, Guo R, Liu X, Jones SN, Yen Y (November 2008). "ATM-mediated serine 72 phosphorylation stabilizes ribonucleotide reductase small subunit p53R2 protein against MDM2 to DNA damage". Proc. Natl. Acad. Sci. U.S.A. 105 (47): 18519–24.  
  47. ^ Chen D, Zhang J, Li M, Rayburn ER, Wang H, Zhang R (February 2009). "RYBP stabilizes p53 by modulating MDM2". EMBO Rep. 10 (2): 166–72.  
  48. ^ Léveillard T, Wasylyk B (December 1997). "The MDM2 C-terminal region binds to TAFII250 and is required for MDM2 regulation of the cyclin A promoter". J. Biol. Chem. 272 (49): 30651–61.  
  49. ^ Thut CJ, Goodrich JA, Tjian R (August 1997). "Repression of p53-mediated transcription by MDM2: a dual mechanism". Genes Dev. 11 (15): 1974–86.  
  50. ^ Song MS, Song SJ, Kim SY, Oh HJ, Lim DS (July 2008). "The tumour suppressor RASSF1A promotes MDM2 self-ubiquitination by disrupting the MDM2-DAXX-HAUSP complex". EMBO J. 27 (13): 1863–74.  
  51. ^ Yang W, Dicker DT, Chen J, El-Deiry WS (March 2008). "CARPs enhance p53 turnover by degrading 14-3-3sigma and stabilizing MDM2". Cell Cycle 7 (5): 670–82.  

Further reading

  • Cahilly-Snyder L, Yang-Feng T, Francke U, George DL (May 1987). "Molecular analysis and chromosomal mapping of amplified genes isolated from a transformed mouse 3T3 cell line". Somat. Cell Mol. Genet. 13 (3): 235–44.  
  • Chen J, Lin J, Levine AJ (January 1995). "Regulation of transcription functions of the p53 tumor suppressor by the mdm-2 oncogene". Mol. Med. 1 (2): 142–52.  
  • Fang S, Jensen JP, Ludwig RL, Vousden KH, Weissman AM (March 2000). "Mdm2 is a RING finger-dependent ubiquitin protein ligase for itself and p53". J. Biol. Chem. 275 (12): 8945–51.  
  • Freedman DA, Wu L, Levine AJ (January 1999). "Functions of the MDM2 oncoprotein". Cell. Mol. Life Sci. 55 (1): 96–107.  
  • Hay TJ, Meek DW (July 2000). "Multiple sites of in vivo phosphorylation in the MDM2 oncoprotein cluster within two important functional domains". FEBS Lett. 478 (1-2): 183–6.  
  • Honda R, Tanaka H, Yasuda H (December 1997). "Oncoprotein MDM2 is a ubiquitin ligase E3 for tumor suppressor p53". FEBS Lett. 420 (1): 25–7.  
  • Honda R, Yasuda H (March 2000). "Activity of MDM2, a ubiquitin ligase, toward p53 or itself is dependent on the RING finger domain of the ligase". Oncogene 19 (11): 1473–6.  
  • Kubbutat MH, Jones SN, Vousden KH (May 1997). "Regulation of p53 stability by Mdm2". Nature 387 (6630): 299–303.  
  • Kussie PH, Gorina S, Marechal V, Elenbaas B, Moreau J, Levine AJ, Pavletich NP (November 1996). "Structure of the MDM2 oncoprotein bound to the p53 tumor suppressor transactivation domain". Science 274 (5289): 948–53.  
  • Meek DW, Knippschild U (December 2003). "Posttranslational modification of MDM2". Mol. Cancer Res. 1 (14): 1017–26.  
  • Midgley CA, Desterro JM, Saville MK, Howard S, Sparks A, Hay RT, Lane DP (May 2000). "An N-terminal p14ARF peptide blocks Mdm2-dependent ubiquitination in vitro and can activate p53 in vivo". Oncogene 19 (19): 2312–23.  
  • Momand J, Wu HH, Dasgupta G (January 2000). "MDM2--master regulator of the p53 tumor suppressor protein". Gene 242 (1-2): 15–29.  
  • Momand J, Zambetti GP, Olson DC, George D, Levine AJ (June 1992). "The mdm-2 oncogene product forms a complex with the p53 protein and inhibits p53-mediated transactivation". Cell 69 (7): 1237–45.  
  • Shieh SY, Ikeda M, Taya Y, Prives C (October 1997). "DNA damage-induced phosphorylation of p53 alleviates inhibition by MDM2". Cell 91 (3): 325–34.  
  • Tao W, Levine AJ (June 1999). "P19(ARF) stabilizes p53 by blocking nucleo-cytoplasmic shuttling of Mdm2". Proc. Natl. Acad. Sci. U.S.A. 96 (12): 6937–41.  
  • Tao W, Levine AJ (March 1999). "Nucleocytoplasmic shuttling of oncoprotein Hdm2 is required for Hdm2-mediated degradation of p53". Proc. Natl. Acad. Sci. U.S.A. 96 (6): 3077–80.  

External links

  • NLM
  • NCBI-Gene
  • Nextbio
  • Genecards
  • Atlas of Genetics
This article was sourced from Creative Commons Attribution-ShareAlike License; additional terms may apply. World Heritage Encyclopedia content is assembled from numerous content providers, Open Access Publishing, and in compliance with The Fair Access to Science and Technology Research Act (FASTR), Wikimedia Foundation, Inc., Public Library of Science, The Encyclopedia of Life, Open Book Publishers (OBP), PubMed, U.S. National Library of Medicine, National Center for Biotechnology Information, U.S. National Library of Medicine, National Institutes of Health (NIH), U.S. Department of Health & Human Services, and, which sources content from all federal, state, local, tribal, and territorial government publication portals (.gov, .mil, .edu). Funding for and content contributors is made possible from the U.S. Congress, E-Government Act of 2002.
Crowd sourced content that is contributed to World Heritage Encyclopedia is peer reviewed and edited by our editorial staff to ensure quality scholarly research articles.
By using this site, you agree to the Terms of Use and Privacy Policy. World Heritage Encyclopedia™ is a registered trademark of the World Public Library Association, a non-profit organization.

Copyright © World Library Foundation. All rights reserved. eBooks from Project Gutenberg are sponsored by the World Library Foundation,
a 501c(4) Member's Support Non-Profit Organization, and is NOT affiliated with any governmental agency or department.