NF-kappaB regulates the stability and activity of p73 by inducing its proteolytic degradation through a ubiquitin-dependent proteasome pathway.
Nuclear factor kappa B (NF-kappaB), which exists as heterodimeric complexes composed of p50 and p65, has been shown to play an important role in cell survival processes. In the present study, we found for the first time that NF-kappaB has an ability to induce the ubiquitin-dependent proteasomal degradation of proapoptotic p73alpha. The activation of NF-kappaB in tumor necrosis factor alpha (TNF-alpha)-stimulated H1299 cells resulted in a significant reduction in the amounts of the endogenous p73alpha. Consistent with these results, TNF-alpha-mediated downregulation of p73alpha was observed in wild-type (WT) mouse embryonic fibroblasts (MEFs) but not in p65-deficient MEFs. Ectopic expression of NF-kappaB decreased a half-life of p73alpha by increasing its ubiquitination levels, and thereby inhibiting the transcriptional activity as well as proapoptotic function of p73alpha, whereas NF-kappaB had undetectable effects on p53. Immunoprecipitation experiments demonstrated that, under our experimental conditions, NF-kappaB does not bind to p73alpha in mammalian cultured cells. In contrast to WT p65, the COOH-terminal deletion mutant of p65 (p65DeltaC) failed to reduce the expression levels of p73alpha, suggesting that NF-kappaB-mediated proteolytic degradation of p73alpha requires the transcriptional activity of NF-kappaB. Taken together, our present results imply that NF-kappaB-mediated degradation of proapoptotic p73 is a novel inhibitory mechanism of p73 that regulates cell survival and death.
Kikuchi
H
H
Division of Biochemistry, Chiba Cancer Center Research Institute, Chiba, Japan.
Ozaki
T
T
Furuya
K
K
Hanamoto
T
T
Nakanishi
M
M
Yamamoto
H
H
Yoshida
K
K
Todo
S
S
Nakagawara
A
A
D000818:Animals; D019556:COS Cells; D045744:Cell Line, Tumor; D002522:Chlorocebus aethiops; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015536:Down-Regulation; D004622:Embryo, Mammalian / Q000166:cytology; D005347:Fibroblasts / Q000378:metabolism; D017353:Gene Deletion; D006801:Humans; D051379:Mice; D016328:NF-kappa B / Q000378:metabolism*; D052002:NF-kappa B p50 Subunit / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins / Q000378:metabolism*; D046988:Proteasome Endopeptidase Complex / Q000378:metabolism*; D011499:Protein Processing, Post-Translational; D050863:Synaptotagmin I / Q000235:genetics; D051996:Transcription Factor RelA / Q000235:genetics / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism / Q000494:pharmacology; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins / Q000378:metabolism*; D025801:Ubiquitin / Q000378:metabolism*
D004268:DNA-Binding Proteins; D016328:NF-kappa B; D052002:NF-kappa B p50 Subunit; D009687:Nuclear Proteins; D050863:Synaptotagmin I; C000606460:TP73 protein, human; D051996:Transcription Factor RelA; C000606368:Trp73 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D000072160:Tumor Protein p73; D025521:Tumor Suppressor Proteins; D025801:Ubiquitin; D046988:Proteasome Endopeptidase Complex