COP9 signalosome-specific phosphorylation targets p53 to degradation by the ubiquitin system

Abstract

In higher eukaryotic cells, the p53 protein is degraded by the ubiquitin-26S proteasome system mediated by Mdm2 or the human papilloma virus E6 protein. Here we show that COP9 signalosome (CSN)-specific phosphorylation targets human p53 to ubiquitin-26S proteasome-dependent degradation. As visualized by electron microscopy, p53 binds with high affinity to the native CSN complex. p53 interacts via its N-terminus with CSN subunit 5/Jab1 as shown by far-western and pull-down assays. The CSN-specific phosphorylation sites were mapped to the core domain of p53 including Thr155. A phosphorylated peptide, Deltap53(145-164), specifically inhibits CSN-mediated phosphorylation and p53 degradation. Curcumin, a CSN kinase inhibitor, blocks E6-dependent p53 degradation in reticulocyte lysates. Mutation of Thr155 to valine is sufficient to stabilize p53 against E6-dependent degradation in reticulocyte lysates and to reduce binding to Mdm2. The p53T155V mutant accumulates in both HeLa and HL 60 cells and exhibits a mutant (PAb 240+) conformation. It induces the cyclin-dependent inhibitor p21. In HeLa and MCF-7 cells, inhibition of CSN kinase by curcumin or Deltap53(145-164) results in accumulation of endogenous p53.

Role for casein kinase 2 in the regulation of HIF‐1 activity

“…On the other hand, it has to be noted that CK2 phosphorylation of p53 on T155 destabilizes the protein. 65 An inhibition of this process, for example by DRB, would thus result in more p53 and less HIF-1 activity, which is observed in this work.…”

Jab1 is overexpressed in human breast cancer and is a downstream target for HER-2/neu

“…4 Jab1 may trigger the proteolysis of the tumor suppressor p53 and exhibit tumor-promoting activity in cells. 26 In addition, Jab1 interacts directly with Smad4 and induces its degradation via the ubiquitin/ proteasome pathway which leads to attenuation of transforming growth factor-b-induced gene transcription. 27 Because transforming growth factor-b exhibits anti-cancer activity in the early stages of tumorigenesis, inhibition of transforming growth factor-b signaling pathway by Jab1 may promote tumor formation.…”

The COP9 signalosome-mediated deneddylation is stimulated by caspases during apoptosis

“…Cell lysis and Western blotting 4 Cells were washed twice with ice-cold PBS and lyzed in triple-detergent lysis buffer [14].…”

“…However, its role in apoptosis is unknown. Although the UPS and the CSN determine the stability of regulatory molecules involved in apoptosis such as p53, Bax, Bak and Smac [13][14][15], the exact function of the system in programmed cell death is still obscure. Inhibitors of CSN-associated kinases induce accumulation of p53 and apoptosis in tumor cells [16].…”