Ubiquitin-specific peptidase 48 regulates Mdm2 protein levels independent of its deubiquitinase activity.

The overexpression of Mdm2 has been linked to the loss of p53 tumour suppressor activity in several human cancers. Here, we present results suggesting that ubiquitin-specific peptidase 48 (USP48), a deubiquitinase that has been linked in previous reports to the NF-κB signaling pathway, is a novel Mdm2 binding partner that promotes Mdm2 stability and enhances Mdm2-mediated p53 ubiquitination and degradation. In contrast to other deubiquitinating enzymes (DUBs) that have been previously implicated in the regulation of Mdm2 protein stability, USP48 did not induce Mdm2 stabilization by significantly reducing Mdm2 ubiquitination levels.

A Novel Interaction between TFII-I and Mdm2 with a Negative Effect on TFII-I Transcriptional Activity.

Williams-Beuren syndrome-associated transcription factor TFII-I plays a critical regulatory role in bone and neural tissue development and in immunity, in part by regulating cell proliferation in response to mitogens. Mdm2, a cellular oncogene responsible for the loss of p53 tumor suppressor activity in a significant proportion of human cancers, was identified in this study as a new binding partner for TFII-I and a negative regulator of TFII-I-mediated transcription. These findings suggest a new p53-independent mechanism by which increased Mdm2 levels found in human tumors could influence cancer cells.

MDM2 polymorphism associated with the development of cervical lesions in women infected with Human papillomavirus and using of oral contraceptives.

Background: The MDM2 gene is the major negative regulator of p53, a tumor suppressor protein. Single nucleotide polymorphism in promoter region of MDM2 gene leads to increased expression resulting in higher levels of MDM2 protein. This event increases the attenuation of the p53 pathway.

Mammalian DIS3L2 exoribonuclease targets the uridylated precursors of let-7 miRNAs.

The mechanisms of gene expression regulation by miRNAs have been extensively studied. However, the regulation of miRNA function and decay has long remained enigmatic. Only recently, 3' uridylation via LIN28A-TUT4/7 has been recognized as an essential component controlling the biogenesis of let-7 miRNAs in stem cells.

Mutational analysis reveals a dual role of Mdm2 acidic domain in the regulation of p53 stability.

The exact role of the central acidic domain of Mdm2 in p53 degradation remains unclear. We therefore performed a systematic and comprehensive analysis of the acidic domain using a series of short deletions and found that only a minor part of the domain was indispensable for Mdm2-mediated p53 ubiquitylation. Moreover, we identified a short stretch of acidic amino acids required for p53 degradation but not ubiquitylation, indicating that, in addition to p53 ubiquitylation, the acidic domain might be involved in a critical post-ubiquitylation step in p53 degradation.

Mutational analysis of Mdm2 C-terminal tail suggests an evolutionarily conserved role of its length in Mdm2 activity toward p53 and indicates structural differences between Mdm2 homodimers and Mdm2/MdmX heterodimers.

Mdm2 can mediate p53 ubiquitylation and degradation either in the form of the Mdm2 homodimer or Mdm2/MdmX heterodimer. The ubiquitin ligase activity of these complexes resides mainly in their respective RING finger domains and also requires adjacent C-terminal tails. So far, structural studies have failed to show significant differences between Mdm2 RING homodimers and Mdm2/MdmX RING heterodimers.