Phosphorylation of p53 by IkappaB kinase 2 promotes its degradation by beta-TrCP

• Published in: Proceedings of the National Academy of Sciences - PNAS 2009-02, Vol.106 (8), p.2629-2634
• Main Authors: Xia, Yifeng, Padre, Roanna C, De Mendoza, Tatiana Hurtado, Bottero, Virginie, Tergaonkar, Vinay B, Verma, Inder M
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; beta-Transducin Repeat-Containing Proteins - metabolism; DNA Primers; Hydrolysis; I-kappa B Kinase - metabolism; Mice; Peptide Mapping; Phosphorylation; Protein Binding; RNA, Small Interfering; Tumor Suppressor Protein p53 - metabolism; Ubiquitination
• ISSN: 1091-6490
• DOI: 10.1073/pnas.0812256106

Functional inactivation of p53 and constitutive activation of the NF-kappaB pathway has been associated with several human cancers. In this study, we show that IkappaB kinase 2 (IKK2/IKKbeta), which is critical for NF-kappaB activation, also phosphorylates p53. Phosphorylation of p53 at serines 362 and 366 by IKK2 leads to its recruitment to and ubiquitination by beta-TrCP1. Degradation of ubiquitinated p53 is independent of Mdm2, because it occurs in both wild-type and Mdm2(-/-) cells. SiRNA-mediated reduction in the levels of beta-TrCP1 and other members of the SCF(beta-TrCP1)E3 ubiquitin ligase complex or overexpression of a dominant negative form of beta-TrCP1 enhances p53 stability. Substitutions at Ser-362 and 366 of p53 by alanines (p53 AA) result in reduced phosphorylation of p53 by IKK2, decreased association with beta-TrCP1, and thus increased stability of p53 and expression of p53 target genes such as p21, altering the G1 phase of the cell cycle. Our results identify IKK2 and beta-TrCP1 as novel regulators of the p53 pathway and suggest that blocking of IKK2 and beta-TrCP1 could be a means of regulating p53 stability and thereby modulating its biological activity.