MDM2 Recombinant Protein

This gene encodes a nuclear-localized E3 ubiquitin ligase. The encoded protein can promote tumor formation by targeting tumor suppressor proteins, such as p53, for proteasomal degradation. This gene is itself transcriptionally-regulated by p53. Overexpression or amplification of this locus is detected in a variety of different cancers. There is a pseudogene for this gene on chromosome 2. Alternative splicing results in a multitude of transcript variants, many of which may be expressed only in tumor cells. [provided by RefSeq, Jun 2013]

Function: E3 ubiquitin-protein ligase that mediates ubiquitination of p53/TP53, leading to its degradation by the proteasome. Inhibits p53/TP53- and p73/TP73-mediated cell cycle arrest and apoptosis by binding its transcriptional activation domain. Also acts as an ubiquitin ligase E3 toward itself and ARRB1. Permits the nuclear export of p53/TP53. Promotes proteasome-dependent ubiquitin-independent degradation of retinoblastoma RB1 protein. Inhibits DAXX-mediated apoptosis by inducing its ubiquitination and degradation. Component of the TRIM28/KAP1-MDM2-p53/TP53 complex involved in stabilizing p53/TP53. Also component of the TRIM28/KAP1-ERBB4-MDM2 complex which links growth factor and DNA damage response pathways. Mediates ubiquitination and subsequent proteasome degradation of DYRK2 in nucleus. Ubiquitinates IGF1R and SNAI1 and promotes them to proteasomal degradation. Ref.23 Ref.27 Ref.28 Ref.31 Ref.32 Ref.36 Ref.43 Ref.46 Ref.48 Ref.49 Ref.50 Ref.51 Ref.53

Subunit structure: Binds p53/TP53, TP73/p73, ARF/P14, PML, RBL5 and RP11, and specifically to RNA. Can interact with RB1, E1A-associated protein EP300 and the E2F1 transcription factor. Forms a ternary complex with p53/TP53 and WWOX. Interacts with CDKN2AIP, MTBP, RFWD3, TBRG1, USP7, PYHIN1, UBXN6, and RBBP6. Isoform Mdm2-F does not interact with p53/TP53. Interacts with and ubiquitinates HIV-1 Tat. Interacts with ARRB1 and ARRB2. Interacts (isoform 2) with PSMA3. Found in a trimeric complex with MDM2, MDM4 and UPB2. Interacts with USP2 (via N-terminus and C-terminus). Interacts with MDM4. Part of a complex with MDM2, DAXX, RASSF1 and USP7. Part of a complex with DAXX, MDM2 and USP7. Interacts directly with DAXX and USP7. Interacts (via C-terminus) with RASSF1 isoform A (via N-terminus); the interaction is independent of TP53. Interacts with APEX1; leading to its ubiquitination and degradation. Interacts with RYBP; this inhibits ubiquitination of TP53. Identified in a complex with RYBP and p53/TP53. Also component of the TRIM28/KAP1-MDM2-p53/TP53 complex involved in regulating p53/TP53 stabilization and activity. Binds directly both p53/TP53 and TRIM28. Component of the TRIM28/KAP1-ERBB4-MDM2 complex involved in connecting growth factor responses with DNA damage. Interacts directly with both TRIM28 and ERBB4 in the complex. Interacts with DYRK2. Interacts with IGF1R. Interacts with TRIM13; the interaction ubiquitinates MDM2 leading to its proteasomal degradation. Interacts with SNAI1; this interaction promotes SNAI1 ubiquitination. Interacts with NOTCH1 (via intracellular domain). Interacts with FHIT. Interacts with herpes virus 8 protein v-IRF4. Ref.4 Ref.14 Ref.22 Ref.23 Ref.24 Ref.26 Ref.27 Ref.28 Ref.29 Ref.30 Ref.31 Ref.32 Ref.33 Ref.34 Ref.35 Ref.36 Ref.38 Ref.39 Ref.40 Ref.41 Ref.43 Ref.45 Ref.46 Ref.48 Ref.49 Ref.50 Ref.51 Ref.52 Ref.53 Ref.54 Ref.55 Ref.57 Ref.58

Subcellular location: Nucleus › nucleoplasm. Cytoplasm. Nucleus › nucleolus. Note: Expressed predominantly in the nucleoplasm. Interaction with ARF(P14) results in the localization of both proteins to the nucleolus. The nucleolar localization signals in both ARF(P14) and MDM2 may be necessary to allow efficient nucleolar localization of both proteins. Colocalizes with RASSF1 isoform A in the nucleus. Ref.14 Ref.28 Ref.34 Ref.40 Ref.50 Ref.55

Tissue specificity: Ubiquitous. Isoform Mdm2-A, isoform Mdm2-B, isoform Mdm2-C, isoform Mdm2-D, isoform Mdm2-E, isoform Mdm2-F and isoform Mdm2-G are observed in a range of cancers but absent in normal tissues.

Induction: By DNA damage.

Domain: Region I is sufficient for binding p53 and inhibiting its G1 arrest and apoptosis functions. It also binds p73 and E2F1. Region II contains most of a central acidic region required for interaction with ribosomal protein L5 and a putative C4-type zinc finger. The RING finger domain which coordinates two molecules of zinc interacts specifically with RNA whether or not zinc is present and mediates the heterooligomerization with MDM4. It is also essential for its ubiquitin ligase E3 activity toward p53 and itself.

Post-translational modification: Phosphorylation on Ser-166 by SGK1 activates ubiquitination of p53/TP53. Phosphorylated at multiple sites near the RING domain by ATM upon DNA damage; this prevents oligomerization and E3 ligase processivity and impedes constitutive p53/TP53 degradation. Ref.17 Ref.21 Ref.42 Ref.44Auto-ubiquitinated; which leads to proteasomal degradation. Also ubiquitinated by TRIM13. Deubiquitinated by USP2 leads to its accumulation and increases deubiquitination and degradation of p53/TP53. Deubiquitinated by USP7 leading to its stabilization.

Polymorphism: A polymorphism in the MDM2 promoter is associated with susceptibility to accelerated tumor formation in both hereditary and sporadic cancers [

MIM:614401]. It also contributes to susceptibility to Li-Fraumeni syndrome, in patients carrying a TP53 germline mutation.

Involvement in disease: Seems to be amplified in certain tumors (including soft tissue sarcomas, osteosarcomas and gliomas). A higher frequency of splice variants lacking p53 binding domain sequences was found in late-stage and high-grade ovarian and bladder carcinomas. Four of the splice variants show loss of p53 binding.

Miscellaneous: MDM2 RING finger mutations that failed to ubiquitinate p53 in vitro did not target p53 for degradation when expressed in cells.

Sequence similarities: Belongs to the MDM2/MDM4 family.Contains 1 RanBP2-type zinc finger.Contains 1 RING-type zinc finger.Contains 1 SWIB domain.