title: Phosphorylation of p53 by IkappaB kinase 2 promotes its degradation by beta-TrCP.
abstract: 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.
authors.affiliation: Laboratory of Genetics, The Salk Institute for Biological Studies, La Jolla, CA 92037, USA.
authors.forename: Yifeng
authors.initials: Y
authors.lastname: Xia
authors.forename: Roanna C
authors.initials: RC
authors.lastname: Padre
authors.forename: Tatiana Hurtado
authors.initials: TH
authors.lastname: De Mendoza
authors.forename: Virginie
authors.initials: V
authors.lastname: Bottero
authors.forename: Vinay B
authors.initials: VB
authors.lastname: Tergaonkar
authors.forename: Inder M
authors.initials: IM
authors.lastname: Verma
mesh_terms: D000818:Animals; D001483:Base Sequence; D017931:DNA Primers; D006868:Hydrolysis; D051550:I-kappa B Kinase / Q000378:metabolism*; D051379:Mice; D010449:Peptide Mapping; D010766:Phosphorylation; D011485:Protein Binding; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism*; D054875:Ubiquitination; D044844:beta-Transducin Repeat-Containing Proteins / Q000378:metabolism*
chemical_list: D017931:DNA Primers; D034741:RNA, Small Interfering; D016159:Tumor Suppressor Protein p53; D044844:beta-Transducin Repeat-Containing Proteins; D051550:I-kappa B Kinase