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)

This study investigates the mechanism of hormonal regulation of p53 gene expression in MCF-7 human breast cancer cells. 17beta-Estradiol (E2) induced a 2-fold increase in p53 mRNA levels and a 2- to 3-fold increase in p53 protein. Analysis of the p53 gene promoter has identified a minimal E2-responsive region at -106 to -40, and mutation/deletion analysis of the promoter showed that motifs that bind CCAAT-binding transcription factor-1 (CTF-1) and nuclear factor kappaB (NFkappaB) proteins are required for hormone responsiveness. The p65 subunit of NFkappaB was identified in both nuclear and cytosolic fractions of untreated MCF-7 cells; however, formation of the nuclear NFkappaB complex was E2 independent. Hormonal activation of constructs containing p53 promoter inserts (-106 to -40) and the GAL4-p65 fusion proteins was inhibited by the intracellular Ca2+ ion chelator EGTA-AM and Ca2+/calmodulin-dependent protein kinase (CaMK) inhibitor KN-93. Constitutively active CaMKIV but not CaMKI activated p65, and treatment of MCF-7 cells with E2 induced phosphorylation of CaMKIV but not CaMKI. The results indicate that hormonal activation of p53 though nongenomic pathways was CaMKIV-dependent and involved cooperative p65-CTF-1 interactions.
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PMID:Estrogen up-regulation of p53 gene expression in MCF-7 breast cancer cells is mediated by calmodulin kinase IV-dependent activation of a nuclear factor kappaB/CCAAT-binding transcription factor-1 complex. 1214 35

p63 is a transcription factor structurally related to the p53 tumor suppressor. The C-terminal region differs from p53's in that it contains a sterile alpha motif (SAM) domain and is subject to multiple alternative splicings. The N-terminal region is present in the transactivation (TA) and DeltaN configurations, with the latter lacking the transcriptional activation domain 1. Single amino acid substitutions and frameshift mutations of p63 cause the human ankyloblepharon ectodermal dysplasia clefting (AEC) or ectrodactyly ectodermal dysplasia and facial clefting (EEC) syndromes. We have systematically compared the activities of the wild-type p63 isoforms and of the natural mutants in activation and repression assays on three promoters modulated by p53. We found that p63 proteins with an altered SAM domain or no SAM domain-the beta isoforms, the EEC frameshift mutant, and the missense AEC mutations-all showed a distinctly higher level of activation of the MDM2 promoter and decreased repression on the HSP70 promoter. Fusion of SAM to the GAL4 DNA-binding domain repressed a heterologous promoter. A second activation domain, TA2, corresponding to exons 11 to 12, was uncovered by comparing the activation of DeltaN isoforms on natural promoters and in GAL4 fusion systems. In colony formation assays, the AEC mutants, but not the EEC frameshift, were consistently less efficient in suppressing growth, in both the TA version and the DeltaN version, with respect to their p63alpha counterparts. These data highlight the modularity of p63, identifying the SAM domain as a dominant transcriptional repression module and indicating that the AEC and EEC frameshift mutants are characterized by a subversion of the p63 transcriptional potential.
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PMID:Complex transcriptional effects of p63 isoforms: identification of novel activation and repression domains. 1244 84

Reconstitution of the stages in the assembly of the p300.p53 transcription complex has identified a novel type of DNA-dependent regulation of p300-catalyzed acetylation. Phosphorylation at the CHK2 site (Ser(20)) in the N-terminal activation domain of p53 stabilized p300 binding. The phosphopeptide binding activity of p300 was mapped in vitro to two domains: the C-terminal IBiD domain and the N-terminal IHD domain (IBiD homology domain). The IHD or IBiD minidomains can bind to the p53 activation domain in vivo as determined using the mammalian two-hybrid VP16-GAL4 luciferase reporter assay. The IHD and IBiD minidomains of p300 also functioned as dominant negative inhibitors of p53-dependent transcription in vivo. Upon examining the affects of p300 binding on substrate acetylation, we found that the p53 consensus site DNA promotes a striking increase in p53 acetylation in vitro. Co-transfection into cells of the p53 gene and plasmid DNA containing the consensus DNA binding site of p53 activated DNA-dependent acetylation of p53 in vivo. The phosphopeptide binding activity of p300 is critical for DNA-dependent acetylation, as p53 acetylation was inhibited by phospho-Ser(20) peptides. Consensus site DNA-dependent acetylation of p53 stabilized the p300.p53 protein complex, whereas basal acetylation of p53 by p300 in the presence of nonspecific DNA resulted in p300 dissociation. These data identify at least three distinct stages in the assembly of a p300.p53 complex: 1) p300 docking to the activation domain of p53 via the IBiD and/or IHD domains; 2) DNA-dependent acetylation of p53; and 3) stabilization of the p300.p53(AC) complex after acetylation. The ability of DNA to act as an allosteric ligand to activate substrate acetylation identifies a conformational constraint that can be placed on the p300-acetylation reaction that is likely to be an amplification signal and influence protein-protein contacts at a promoter.
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PMID:DNA-dependent acetylation of p53 by the transcription coactivator p300. 1249 68

The functional effect of the interaction of E2F1 and hepatitis B virus X protein (HBx) on the promoter of human p53 gene was studied using chloramphenicol acetyl transferase (CAT) assay. E2F1 activated the p53 promoter through E2F1 binding site. As previously reported, HBx repressed the p53 promoter through E-box. When E2F1 was cotransfected with HBx, E2F1 overcame the repressive effect of HBx on the p53 promoter through the E2F1 site. However, in the thymidine kinase (tk) heterologous promoter system with the E2F1 binding sites, cotransfection of E2F1 and HBx showed a strong synergistic activation. An in vitro interaction assay showed that E2F1 and HBx physically bind with each other. Analyses of the interaction domain with the GAL4 fusion protein showed that the pRb-binding domain of E2F1 was necessary for the functional interaction of these two proteins. Taken together, these results imply the functional inhibitory action of E2F1 on the HBV life cycle and HBV-mediated hepatocellular carcinogenesis (HCC). Therefore, the normal or enhanced function of E2F1 gene would be important in controlling the HBx function in HCC.
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PMID:E2F1 activates the human p53 promoter and overcomes the repressive effect of hepatitis B viral X protein (Hbx) on the p53 promoter. 1262 70

The tumor suppressor protein PML and oncoprotein MDM2 have opposing effects on p53. PML stimulates p53 activity by recruiting it to nuclear foci termed PML nuclear bodies. In contrast, MDM2 inhibits p53 by promoting its degradation. To date, neither a physical nor functional relationship between PML and MDM2 has been described. In this study, we report an in vivo and in vitro interaction between PML and MDM2 which is independent of p53. Two separate regions of PML are recognized which can interact with MDM2. The C-terminal half of PML, encoded by residues 300-633, can interact with the central region of MDM2 which includes the MDM2 acidic domain. In addition, PML amino acids 1-200, which encode the RING-finger and most of the B box zinc binding motifs, can interact with the C-terminal, RING-finger containing region of MDM2. Interestingly, PML mutants in which sumoylation at lysine 160 was inhibited displayed an increased association with MDM2, suggesting that sumoylation at this site may be a determinant of PML-MDM2 binding. Coexpression with MDM2 caused a redistribution of PML from the nucleus to the cytoplasm, and this required the PML N terminus and the MDM2 RING-finger domain. These results suggest that interaction between the PML N terminus and MDM2 C terminus can promote PML nuclear exclusion. Wild-type MDM2 inhibited the ability of PML to stimulate the transcriptional activity of a GAL4-CBP fusion protein. This inhibition required the central, acidic region of MDM2, but did not require the MDM2 C terminus. Taken together, these studies demonstrate that MDM2 and PML can interact through at least two separate protein regions, and that these interactions can have specific effects on the activity and/or localization of PML.
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PMID:Physical and functional interactions between PML and MDM2. 1275 44

Adenoviral gene expression that is repressed by p53 in nontransformed cells could provide a tumor-specific gene therapy approach for a large subset of tumors. Adenoviral infection in vivo induces stabilization of p53, which can be utilized for a strategy that includes p53-dependent expression of a transcriptional repressor and a target promoter,which is highly susceptible for transcriptional repression. Therefore, we constructed different versions of CMV-promoters (CMVgal) with binding sites for GAL4-DBD and investigated 11 GAL4-DBD fusion proteins to elucidate the most effective repressor domain to silence CMVgal activity. The transcriptional repressor GAL4-KRAB-A under control of a p53-dependent promoter facilitates strong CMVgal-mediated gene expression specifically in p53 mutant cells by a double-recombinant adenoviral vector (Ad-RGCdR). GAL4-KRAB-A mediates strong transcriptional repression of Ad-RGCdR in p53 wild-type cells, which could be further enhanced by preactivation of p53-signalling following low-dose chemotherapy prior to adenoviral infection. By utilizing p53 signalling involved in chemotherapy and adenoviral infection, more than 99% of Ad-RGCdR gene expression could be repressed in p53 wild-type cells. Controlled gene expression from CMVgal promoters by transcriptional repression utilizing functional p53 signalling thus provides a very effective tool for tumor-specific adenoviral gene therapy.
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PMID:Tumor-specific adenoviral gene therapy: transcriptional repression of gene expression by utilizing p53-signal transduction pathways. 1468 24

Nemo-like kinase (NLK) is a serine/threonine kinase that suppresses the transcription activity of the beta-catenin-T-cell factor (TCF) complex through phosphorylation of TCF. Our previous study showed that NLK overexpression induces apoptosis in DLD-1 human colon cancer cells and that apoptosis induction presumably requires a mechanism other than the suppression of beta-catenin-TCF complex. Luciferase reporter gene assay with pNF-kappaB-Luc revealed that NLK could suppress transcription activity of NF-kappaB in a kinase-dependent manner. However, it appeared that transcription co-activators of NF-kappaB, such as CREB binding protein (CBP)/p300, were likely to be the direct targets of NLK, rather than NF-kappaB itself. Luciferase reporter gene analysis of GAL4-CBP fusion proteins revealed that the C-terminal region of CBP was critical for transcription suppression by NLK. In vitro kinase assay showed that NLK could phosphorylate the C-terminal domain of CBP. However, HAT activity was not suppressed by the induction of wild-type NLK in DLD-1 cells. Furthermore, we observed that NLK suppressed the transcription activity of AP-1, Smad, and p53, all of which also utilize CBP as a co-activator. The extent of suppression by NLK was similar among the transcription factors tested (50-60% reduction). Our results suggest that NLK may suppress a wide range of gene expression, possibly through CBP.
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PMID:Nemo-like kinase suppresses a wide range of transcription factors, including nuclear factor-kappaB. 1472 Mar 27

CREB-binding protein (CBP) and p300 contain modular domains that mediate protein-protein interactions with a wide variety of nuclear factors. A C-terminal domain of CBP (referred to as the SID) is responsible for interaction with the alpha-helical AD1 domain of p160 coactivators such as the steroid receptor coactivator (SRC1), and also other transcriptional regulators such as E1A, Ets-2, IRF3, and p53. Here we show that the pointed (PNT) domain of Ets-2 mediates its interaction with the CBP SID, and describe the effects of mutations in the SID on binding of Ets-2, E1A, and SRC1. In vitro binding studies indicate that SRC1, Ets-2 and E1A display mutually exclusive binding to the CBP SID. Consistent with this, we observed negative cross-talk between ERalpha/SRC1, Ets-2, and E1A proteins in reporter assays in transiently transfected cells. Transcriptional inhibition of Ets-2 or GAL4-AD1 activity by E1A was rescued by co-transfection with a CBP expression plasmid, consistent with the hypothesis that the observed inhibition was due to competition for CBP in vivo. Sequence comparisons revealed that SID-binding proteins contain a leucine-rich motif similar to the alpha-helix Aalpha1 of the SRC1 AD1 domain. Deletion mutants of E1A and Ets-2 lacking the conserved motif were unable to bind the CBP SID. Moreover, a peptide corresponding to this sequence competed the binding of full-length SRC1, Ets-2, and E1A proteins to the CBP SID. Thus, a leucine-rich amphipathic alpha-helix mediates mutually exclusive interactions of functionally diverse nuclear proteins with CBP.
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PMID:A Conserved alpha-helical motif mediates the binding of diverse nuclear proteins to the SRC1 interaction domain of CBP. 1472 92

We have previously reported that human matrix metalloproteinase-1 (MMP1) is a p53 target gene subject to down-regulation (Sun et al. [1999]: J Biol Chem 274:11535-11540]. In the present study, we demonstrate that the down-regulation of the human -83MMP1 promoter fragment by p53 was abolished when the -72AP-1 site was eliminated and that a GAL4-cJun-mediated but not a GAL4-Elk1-mediated induction of pFR-luci was effectively inhibited by p53 suggesting an AP-1 dependent but AP-1 binding independent mechanism. Results from gel mobility shift assays were consistent with an AP-1 binding independent mechanism. We also demonstrate that both p300 and TATA box binding proteins cooperated with the transcription factor AP-1 to induce the promoter of MMP1; however, p53 only inhibited the p300-mediated induction of the MMP1 promoter and the inhibition was -72AP-1 dependent. Furthermore, the down-regulation of the MMP1 promoter and mRNA by p53 could be reversed by p300 and by a p53 binding p300 fragment that had no coactivator activity. Taken together, these results indicate that p53 down-regulates MMP1 mainly by disrupting the communications between the transactivator AP-1 and the basal transcriptional complex, which are partially mediated by p300. Finally, by using p53 truncated mutant constructs, we demonstrate that both the N-terminal activation domain and the C-terminal oligomerization domains of p53 were required for the down-regulation of MMP1 transcription.
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PMID:P53 down-regulates matrix metalloproteinase-1 by targeting the communications between AP-1 and the basal transcription complex. 1510 53

The p53 tumor suppressor protein functions via specific gene activation to inhibit passage through the cell cycle and to trigger apoptosis. The p53 protein is homologous to p63 and p73, proteins that regulate transcription via the same promoter sequences but which activate different genes. In this study we tested whether p53, p63, and p73 have different mechanisms of activating transcription and if such a difference could explain how each factor stimulates the transcription of distinct sets of genes. We found that when comparing p53 to the transcriptional activator, GAL4-VP16, both of which are classified as acidic activators, that stimulation of transcription by p53 is dependent upon low Mg2+ concentrations and limiting amounts of extract. By comparison, the stimulation of RNA synthesis by GAL4-VP16 was not dependent on a specific concentration of Mg2+ but did require higher amounts of extract, suggesting that a certain factor not required for p53-dependent gene activation was limiting in the extract. In contrast to the differences between p53 and GAL4-VP16, p63 and p73 both regulated transcription in vitro under similar conditions as did p53. All three proteins, purified to near homogeneity, were equally active in binding to the p53-response element, and equally active in stimulating transcription reactions using naked DNA templates, DNA templates reconstituted in chromatin using histones purified from HeLa cells, or hyper-acetylated histones. These results argue that the gene specificity of p63 and p73 dependent activation of transcription depends upon specific coactivators present in the specific cell types and upon other factors bound to the promoters.
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PMID:The tumor suppressor protein p53 functions similarly to p63 and p73 in activating transcription in vitro. 1590 76


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