Inactivation of the MDM2 RING domain enhances p53 transcriptional activity in mice

Abstract

The MDM2 RING domain harbors E3 ubiquitin ligase activity critical for regulating the degradation of tumor suppressor p53, which controls many cellular pathways. The MDM2 RING domain also is required for an interaction with MDMX. Mice containing a substitution in the MDM2 RING domain, MDM2, disrupting MDM2 E3 function and the MDMX interaction, die during early embryogenesis that can be rescued by p53 deletion. To investigate whether MDM2, which retains p53 binding, has p53-suppressing activity, we generated ; mice, in which we replaced the endogenous alleles with an inducible allele, and compared survival with that of similarly generated ; mice. Adult -null mice died ∼7 days after tamoxifen-induced p53 activation, indicating that in the absence of MDM2, MDMX cannot suppress p53. Surprisingly, ; mice died ∼5 days after tamoxifen injection, suggesting that p53 activity is higher in the presence of MDM2 than in the absence of MDM2. Indeed, in MDM2-expressing mouse tissues and embryonic fibroblasts, p53 exhibited higher transcriptional activity than in those expressing no MDM2 or no MDM2 and MDMX. This observation indicated that MDM2 not only is unable to suppress p53 but may have gained the ability to enhance p53 activity. We also found that p53 acetylation, a measure of p53 transcriptional activity, was higher in the presence of MDM2 than in the absence of MDM2. These results reveal an unexpected role of MDM2 in enhancing p53 activity and suggest the possibility that compounds targeting MDM2 RING domain function could produce even more robust p53 activation.

MALAT1 Activates the P53 Signaling Pathway by Regulating MDM2 to Promote Ischemic Stroke

“…Many studies have shown that MDM2 can enhance p53 activity [27,28]. Moreover, previous investigation has revealed that p53 is a key modulator of cellular stress responses, becoming activated in ischemic areas of the brain and contributing to neuronal apoptosis.…”

How to Inactivate Human Ubiquitin E3 Ligases by Mutation

“…Despite less frequently, in a number of investigations, the Cys involved in zinc coordination have also been efficiently mutated into serine. Indeed, this type of point mutation that results on E3 ligase inactivation has served to uncover, among others, the role of MDM2, RNF8, and SIAH1 RING E3s in cell cycle regulation, DNA damage response and Wnt signalling, respectively (Ji et al, 2017;Tian et al, 2017;Tripathi and Smith, 2017). Additionally, although there are fewer examples, it has been demonstrated that mutating the His into Glu, Tyr or Arg is sufficient to inactivate the ligase activity of MKRN1, RNF2, and RNF43 E3s, respectively (Xia et al, 2014;Loregger et al, 2015;Lee et al, 2018b; Figure 3).…”

Inhibition of the lncRNA MIAT prevents podocyte injury and mitotic catastrophe in diabetic nephropathy

“…Therefore, Sox4 inhibits the ubiquitination of p53. As Mdm2 is a vital protein in mediating podocyte mitotic catastrophe and modulating p53, 29 , 30 , 31 we then analyzed whether Sox4 stabilized p53 by inhibiting in Mdm2-mediated p53 ubiquitination. As shown in Figure 6 G, the p53 protein level was reduced when Mdm2 was cotransfected into podocytes, while its expression was increased with increasing amounts of the Myc-Sox4 plasmid, indicating that the interaction between Sox4 and p53 is pivotal for the inhibitory effect of Sox4 on Mdm2-mediated p53 degradation.…”