Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Although MDM2 plays a major role in regulating the stability of the p53 tumor suppressor protein, other poorly understood MDM2-independent pathways also exist. Human adenoviruses have evolved strategies to regulate p53 function and stability to permit efficient viral replication. One mechanism involves adenovirus E1B55K and E4orf6 proteins, which collaborate to target p53 for degradation. To determine the mechanism of this process, a multiprotein E4orf6-associated complex was purified and shown to contain a novel Cullin-containing E3 ubiquitin ligase that is (1) composed of Cullin family member Cul5, Elongins B and C, and the RING-H2 finger protein Rbx1(ROC1); (2) remarkably similar to the von Hippel-Lindau tumor suppressor and SCF (Skp1-Cul1/Cdc53-F-box) E3 ubiquitin ligase complexes; and (3) capable of stimulating ubiquitination of p53 in vitro in the presence of E1/E2 ubiquitin-activating and -conjugating enzymes. Cullins are activated by NEDD8 modification; therefore, to determine whether Cullin complexes are required for adenovirus-induced p53 degradation, studies were conducted in ts41 Chinese hamster ovary cells that are temperature sensitive for the NEDD8 pathway. E4orf6/E1B55K failed to induce the degradation of p53 at the nonpermissive temperature. Thus, our results identify a novel role for the Cullin-based machinery in regulation of p53.
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PMID:Degradation of p53 by adenovirus E4orf6 and E1B55K proteins occurs via a novel mechanism involving a Cullin-containing complex. 1173 75

APP-BP1, first identified as a protein that interacts with the carboxyl (C) terminus of the amyloid precursor protein (APP), is one-half of the bipartite activating enzyme for the ubiquitin-like protein NEDD8. We report here that APP-BP1 also specifically interacts with apoptosis stimulating protein of p53 ASPP2 in non-transfected cells through the functional predominant N-terminal domain ASPP2(332-483). ASPP2 inhibits the ability of APP-BP1 to rescue the ts41 cell cycle mutation and inhibits APP-BP1 induced apoptosis in primary neurons. ASPP2 reduces the ability of NEDD8 to conjugate to Cullin-1, inhibits APP-BP1-dependent ts41 cell proliferation, and blocks the ability of APP-BP1 to cause apoptosis and to cause DNA synthesis in neurons. We also show that ASPP2 activates nuclear factor-kappaB (NF-kappaB) transcriptional activity, which seems to be inhibited by the neddylation pathway since the dominant negative NEDD8 activating enzyme causes enhanced NF-kappaB activity. Our data provide the first in vivo evidence that ASPP2 is a negative regulator of the neddylation pathway through specific interaction with APP-BP1 and suggest that dysfunction of the APP-BP1 interaction with APP may be one cause of Alzheimer's disease.
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PMID:ASPP2 inhibits APP-BP1-mediated NEDD8 conjugation to cullin-1 and decreases APP-BP1-induced cell proliferation and neuronal apoptosis. 1269 6

The only reported role for the conjugation of the NEDD8 ubiquitin-like molecule is control of the activity of SCF ubiquitin ligase complexes. Here, we show that the Mdm2 RING finger E3 ubiquitin ligase can also promote NEDD8 modification of the p53 tumor suppressor protein. Mdm2 is itself modified with NEDD8 with very similar characteristics to the autoubiquitination activity of Mdm2. By using a cell line (TS-41) with a temperature-sensitive mutation in the NEDD8 conjugation pathway and a p53 mutant that cannot be NEDDylated (3NKR), we demonstrate that Mdm2-dependent NEDD8 modification of p53 inhibits its transcriptional activity. These findings expand the role for Mdm2 as an E3 ligase, providing evidence that Mdm2 is a common component of the ubiquitin and NEDD8 conjugation pathway and indicating the diverse mechanisms by which E3 ligases can control the function of substrate proteins.
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PMID:Mdm2-mediated NEDD8 conjugation of p53 inhibits its transcriptional activity. 1524 38

NEDD8 (neural precursor cell expressed developmentally downregulated gene 8)-specific protease NEDP1 processes preNEDD8 to its mature form and deconjugates NEDD8 from substrates such as p53 and cullins. Although NEDD8 and ubiquitin are highly related in sequence and structure, their attachment to a protein leads to different biological effects. It is therefore critical that NEDP1 discriminates between NEDD8 and ubiquitin, and this requires remarkable precision in molecular recognition. To determine the basis of this specificity, we have determined the crystal structure of NEDP1 in isolation and in a transition state complex with NEDD8. This reveals that NEDP1 is a cysteine protease of the Ulp family. Binding of NEDD8 induces a dramatic conformational change in a flexible loop that swings over the C-terminus of NEDD8 locking it into an extended beta-structure optimal for catalysis. Structural, mutational and biochemical studies have identified key residues involved in molecular recognition. A single-residue difference in the C-terminus of NEDD8 and ubiquitin contributes significantly to the ability of NEDP1 to discriminate between them. In vivo analysis indicates that NEDP1 mutants perturb deNEDDylation of the tumour suppressor p53.
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PMID:Structural basis of NEDD8 ubiquitin discrimination by the deNEDDylating enzyme NEDP1. 1577 60

The function of p73, a transcription factor belonging to the p53 family, is finely regulated by its steady-state protein stability. p73 protein degradation/stabilization can be regulated by mechanisms in part dependent on the ubiquitin proteasome system (UPS): (i) Itch/NEDD4-like UPS degradation, (ii) NEDD8 UPS degradation, and (iii) NQO1 20S proteasome-dependent (but ubiquitin-independent) breakdown. Here, we show that, in vitro, Calpain I can cleave p73 at two distinct sites: the first proline-rich region and within the oligomerization domain. Consequently, different p73 isoforms can be degraded by calpains, i.e., both N-terminal isoforms (TAp73 and DeltaNp73) as well as the C-terminal isoforms (alpha, beta, gamma, delta). Moreover, overexpression of the specific endogenous calpain inhibitor, calpastatin, in cultured cells increased the steady-state p73 level. This suggests that calpains may play a physiological role in the regulation of p73 protein stability.
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PMID:Calpain cleavage regulates the protein stability of p73. 1597 58

Regulation of p53 by the ubiquitin-proteasomal pathway has been studied considerably. Studies have also demonstrated that the ubiquitin-like proteins SUMO-1 and NEDD8 modify p53. Similarly, p63 and p73 are subject to regulation by ubiquitin and ubiquitin-like modifications, and perturbations of these pathways in the regulation of the p53 family have been implicated in tumorigenesis and developmental abnormalities. Here, we provide an overview of the current understanding of the regulation of the p53 family by covalent modification by ubiquitin, SUMO-1, and NEDD8.
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PMID:Ubiquitin and ubiquitin-like modifications of the p53 family. 1692 48

Mutations in p73 are rare in cancer. Emerging evidence suggests that the relative expression of various p73 isoforms may contribute to tumorigenesis. Alternative promoters and N-terminal splicing result in the transcription and processing of either full-length (TA) or N-terminally truncated (deltaN) p73 isoforms. TAp73 possesses pro-apoptotic functions, while deltaNp73 has anti-apoptotic properties via functional inhibition of TAp73 and p53. Here, we report that TAp73, but not deltaNp73, is covalently modified by NEDD8 under physiologic conditions in an Mdm2-dependent manner. Co-expression of NEDP1, a cysteine protease that specifically cleaves NEDD8 conjugates, was shown to deneddylate TAp73. In addition, blockage of the endogenous NEDD8 pathway increased TAp73-mediated transactivation of p53- and p73-responsive promoter-driven reporter activity, and in conjunction, neddylated TAp73 species were found preferentially in the cytoplasm. These results suggest that Mdm2 attenuates TAp73 transactivation function, at least in part, by promoting NEDD8-dependent TAp73 cytoplasmic localization and provide the first evidence of a covalent post-translational modification exclusively targeting the TA isoforms of p73.
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PMID:Mdm2-mediated NEDD8 modification of TAp73 regulates its transactivation function. 1698 Feb 97

CUL7 and the p53-associated, PARkin-like cytoplasmic protein (PARC) were previously reported to form homodimers and heterodimers, the first demonstration of cullin dimerization. Although a CUL7-based SKP1/CUL1/F-box (SCF)-like complex has been observed, little is known about the existence of a PARC-based SCF-like complex and how PARC interacts with CUL7-based complexes. To further characterize PARC-containing complexes, we examined the ability of PARC to form an SCF-like complex. PARC binds RBX1 and is covalently modified by NEDD8, defining PARC as a true cullin. However, PARC fails to bind SKP1 or F-box proteins, including the CUL7-associated FBXW8. To examine the assembly of PARC- and CUL7-containing complexes, tandem affinity purification followed by multidimensional protein identification technology were used. Multidimensional protein identification technology analysis revealed that the CUL7 interaction with FBXW8 was mutually exclusive of CUL7 binding to PARC or p53. Notably, although heterodimers of CUL7 and PARC bind p53, p53 is not required for the dimerization of CUL7 and PARC. The observed physical separation of FBXW8 and PARC is supported functionally by the generation of Parc-/-, Fbxw8-/- mice, which do not show exacerbation of the Fbxw8-/- phenotype. Finally, all of the PARC and CUL7 subcomplexes examined exhibit E3 ubiquitin ligase activity in vitro. Together, these findings indicate that the intricate assembly of PARC- and CUL7-containing complexes is highly regulated, and multiple subcomplexes may exhibit ubiquitin ligase activity.
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PMID:PARC and CUL7 form atypical cullin RING ligase complexes. 1733 28

The tumour suppressor p53 has been shown to be modified at its C-terminus with ubiquitin and the ubiquitin-like proteins SUMO and NEDD8. Whereas monoubiquitination of p53 is strongly associated with nuclear export, the effects of sumoylation and neddylation remain unclear. In this study we have generated p53-Ub, p53-SUMO-1 and p53-NEDD8 fusion proteins as models for the effect of these modifications on the localization and function of p53. As shown before, the ubiquitin fusion clearly drives nuclear export of p53 and we now find that this is also partially the case for a SUMO-1 fusion, which does not localise to PML bodies. In contrast a NEDD8 fusion has little effect on nuclear export, and mutating NEDD8 to more closely resemble ubiquitin did not restore nuclear export. Despite their differing subcellular localization, we find that both p53-ubiquitin and p53-NEDD8 retain similar transcriptional activity and both induce apoptosis at a similar level to unfused p53. The p53-ubiquitin fusion protein is potentially a good model for studying the role of p53 outside the nucleus. However, in our experiments we find that the export of p53 from the nucleus is not sufficient to activate its cytoplasmic apoptotic function which may depend on the ability to deubiquitinate cytoplasmic p53.
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PMID:p53-Ubl fusions as models of ubiquitination, sumoylation and neddylation of p53. 1871 71

Several studies have shown that ribosomal proteins (RPs) are important mediators of p53 activation in response to nucleolar disruption; however, the pathways that control this signalling function of RPs are currently unknown. We have recently shown that RPs are targets for the ubiquitin-like molecule NEDD8, and that NEDDylation protects RPs from destabilization. Here, we identify NEDD8 as a crucial regulator of L11 RP signalling to p53. A decrease in L11 NEDDylation during nucleolar stress causes relocalization of L11 from the nucleolus to the nucleoplasm. This not only provides the signal for p53 activation, but also makes L11 susceptible to degradation. Mouse double minute 2 (MDM2) -mediated NEDDylation protects L11 from degradation and this is required for p53 stabilization during nucleolar stress. By controlling the correct localization and stability of L11, NEDD8 acts as a crucial, new regulator of nucleolar signalling to p53.
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PMID:Regulation of nucleolar signalling to p53 through NEDDylation of L11. 1971 60


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