Acetylation-dependent regulation of MDM2 E3 ligase activity dictates its oncogenic function

Abstract

Abnormal activation of the oncogenic E3 ubiquitin ligase murine double minute 2 (MDM2) is frequently observed in human cancers. By ubiquitinating the tumor suppressor p53 protein, which leads to its proteasome-mediated destruction, MDM2 limits the tumor-suppressing activity of p53. On the other hand, by ubiquitinating itself, MDM2 targets itself for destruction and promotes the p53 tumor suppressor pathway, a process that can be antagonized by the deubiquitinase herpesvirus-associated ubiquitin-specific protease (HAUSP). We investigated the regulation of MDM2 substrate specificity and found that acetyltransferase p300–mediated acetylation and stabilization of MDM2 are molecular switches that block self-ubiquitination, thereby shifting its E3 ligase activity toward p53. In vitro and in cancer cell lines, p300-mediated acetylation of MDM2 on Lys182 and Lys185 enabled HAUSP to bind, presumably deubiquitinate, and stabilize MDM2. This acetylation within the nuclear localization signal domain decreased its interaction with the acidic domain, subsequently increased the interaction between the acidic domain and RING domain in MDM2, enabled the binding of HAUSP to the acidic domain in MDM2, and shifted MDM2 activity from autoubiquitination to p53 ubiquitination. However, upon genotoxic stress through exposure to etoposide, the deacetylase sirtuin 1 (SIRT1) deacetylated MDM2 at Lys182 and Lys185, thereby promoting self-ubiquitination and less ubiquitination and subsequent degradation of p53, thus increasing p53-dependent apoptosis. Therefore, this study indicates that dynamic acetylation is a molecular switch in the regulation of MDM2 substrate specificity, revealing further insight into the posttranslational regulation of the MDM2/p53 cell survival axis.

RETRACTED ARTICLE: Ras-ERK signalling represses H1.4 phosphorylation at serine 36 to promote non-small-cell lung carcinoma cells growth and migration

“…Ras-ERK signalling could degrade PKA by regulating MDM2, indicating Ras-ERK inhibited PKA in a proteasome-dependent manner. It is well-known that MDM2 plays a significant role in proteasome-mediated degradation [18]. However, whether MDM2 directly inhibited PKA function or by mediating other factors are still unclear, which needed to be further studied.…”

“…Further, how PKA was degraded by Ras-ERK signalling was studied. Considering MDM2 is a widely known protein in driving proteasome-mediated degradation [18], we focused on MDM2 for further investigation. Results in Figure 6(A,B) revealed that transfection of cells with an MDM2 expression vector (MDM2-His) remarkably repressed the endogenous and exogenous protein levels of PKA.…”

Degrons in cancer

“…Degradation processes in the p53 pathway add additional layers of complexity because several p53-targeting E3 ligases, including MDM2 and COP1, also have autoubiquitination activity (140,141). Furthermore, genes encoding the E3 ligases COP1, MDM2, PIRH2, and JFK, all of which target p53, are induced by the transcriptional activity of p53 (138,139,(142)(143)(144).…”

Acetylation‐mediated Siah2 stabilization enhances PHD3 degradation in Helicobacter pylori‐infected gastric epithelial cancer cells

“…In mouse, the corresponding residues are K 130 and K 140 (mouse Siah2 GenBank: NP_033200.2). E3 ubiquitin ligase function depends on the acetylation of the "really interesting new gene" domain (23,35). Therefore, we examined the effects of acetylation-null mutations at K 129 and K 139 of Siah2.…”

“…In hypoxia, PHD3 is targeted for degradation by Siah2 (22). It has been recently reported that the function and stability of the E3 ubiquitin ligase mouse double minute 2 are tightly regulated by p300-mediated acetylation (23), wherein acetylation results in reduced self-ubiquitination-mediated degradation of mouse double minute 2. However, the effect of acetylation in regulating Siah function and H. pylori pathogenesis is unknown.…”