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)

hSNF5/Ini1 is a core component of the SWI/SNF complex and the gene is frequently mutated in aggressive pediatric rhabdoid tumors. Mechanisms of the malignant transformation, however, remain poorly understood. We analyzed HeLa cells treated with siRNA to the hSNF5/Ini1 mRNA. The resulting efficient and long-term suppression caused characteristic cell enlargement, cell cycle arrest in G1 phase, and subsequent modest apoptosis. Gene expression profiling of the hSNF5-down-regulated cells by cDNA microarray analysis revealed that a limited number of p53-responsive genes, especially p21, were up-regulated. The p53 protein level was also greatly enhanced, suggesting that loss of hSNF5/Ini1 induces a p53 signaling pathway irrelevant to the chk1/2 phosphorylation pathway. Some rhabdoid tumors with very low or no ARF expression were induced to undergo cell enlargement, growth arrest, and, in one case, apoptosis by ectopic expression of the p14ARF protein. These results may in part account for molecular mechanisms of rhabdoid tumor formation.
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PMID:Knock down of hSNF5/Ini1 causes cell cycle arrest and apoptosis in a p53-dependent manner. 1766 67

S100B protein is one of the factors involved in the down-regulation of tumor suppressor protein p53, a transcription activator that signals for cycle arrest and apoptosis. As the inactivation of normal p53 functions is found in over half of human cancers, restoration of normal p53 functions through the destruction or prevention of S100B--p53 complexes represents a possible approach for the development of anti-cancer drugs. The aim of this work was to propose the S100B binding interface through an examination of the literature and use of molecular modeling (MM) techniques with AutoDock program and the AMBER force field. We propose two residues in the S100B binding pocket (Val56, Phe76) and two residues on the protein surface (Val52, Ala83) are essential for ligand binding. The data presented here indicate that interactions with these four residues are necessary for a reduction in the incidence of the S100B--p53 complex. Additionally, we have tried to explain a mechanism for the action of pentamidine, the best-known S100B ligand, and have proposed two S100B--pentamidine structures. The results presented here may be useful for the efficient design of new S100B ligands.
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PMID:Theoretical study on binding of S100B protein. 1771 98

Brahma (Brm) and Brahma-related gene-1 (Brg1) ATPases share similarities in structure and function, but their presence in human SWI/SNF chromatin remodeling complexes is mutually exclusive. Although Brm and Brg1 can compensate for each other, it is possible that Brm and Brg1 have their unique properties to differentially regulate gene expression in vivo. To explore this, we examined the requirement of Brm and Brg1 for p53-dependent transcription, especially p53-mediated induction of p21 and MDM2, using cell lines in which Brm or Brg1 could be inducibly knocked down. We found that Brg1, but not Brm, is required for p21 induction in MCF7 cells. However, in Brg1-deficient H1299 cells, Brm is also required for p21 induction. Likewise, Brm is necessary for induction of p21 in MCF7 cells in which Brg1 is stably knocked down. In contrast, Brg1 has little, if any, effect on p53-mediated induction of MDM2 in cells that have Brm and vice versa. In addition, we demonstrated that the impaired induction of p21 upon Brg1 knockdown is at least in part due to decreased p53 binding to the p21 promoter. Taken together, we provided evidence that Brg1 is preferentially recruited by p53 for inducing a subset of target genes through chromatin remodeling. Thus, we hypothesize that the potential tumor suppressor function for Brg1 is mediated in part through the p53 pathway.
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PMID:The activity of p53 is differentially regulated by Brm- and Brg1-containing SWI/SNF chromatin remodeling complexes. 1793 76

p53 is a sequence-specific DNA-binding transcription factor and key regulator of cell cycle arrest and apoptosis. p53 is mutated in most human cancers and these mutations generally impair its ability to activate transcription. When expressed in Saccharomyces cerevisiae, p53 acts as a strong transcriptional activator allowing yeast to be used as a model system to study the effects of p53 mutations on activity. However, little is known about the exact mechanisms by which p53 functions in yeast. Using 76 mutant yeast strains, we have evaluated the effect of deleting components of the ADA, COMPASS, INO80, ISW1, Mediator, RSC, SAGA, SAS, SLIK, SWI/SNF, and SWR1 transcriptional regulatory complexes on p53-dependent transcription. In addition, we examined the role of histone H2B ubiquitylation by Rad6/Bre1 on p53 activation. Overall, our analysis indicates that there are several remarkable similarities between p53-dependent transcription in yeast and mammalian cells, suggesting that yeast can serve as a valid model system for at least some aspects of p53 function.
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PMID:Coactivator requirements for p53-dependent transcription in the yeast Saccharomyces cerevisiae. 1795 87

To understand the tumor-suppressing mechanism of the SWI/SNF chromatin remodeling complex, we investigated its molecular relationship with p53. Using the pREP4-luc episomal reporter, we first demonstrated that p53 utilizes the chromatin remodeling activity of the SWI/SNF complex to initiate transcription from the chromatin-structured promoter. Among the components of the SWI/SNF complex, we identified BAF60a as a mediator of the interaction with p53 by the yeast two-hybrid assay. p53 directly interacted only with BAF60a, but not with other components of the SWI/SNF complex, such as BRG1, SRG3, SNF5, or BAF57. We found out that multiple residues at the amino acid 108-150 region of BAF60a were involved in the interaction with the tetramerization domain of p53. The N-terminal fragment of BAF60a containing the p53-interacting region as well as small interfering RNA for baf60a inhibited the SWI/SNF complex-mediated transcriptional activity of p53. The uncoupling of p53 with the SWI/SNF complex resulted in the repression of both p53-dependent apoptosis and cell cycle arrest by the regulation of target genes. These results suggest that the SWI/SNF chromatin remodeling complex is involved in the suppression of tumors by the interaction with p53.
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PMID:BAF60a interacts with p53 to recruit the SWI/SNF complex. 1830 29

Components of the SWI/SNF chromatin-remodeling complex, such as INI1, are inactivated in human cancer and, thus, act as tumor suppressors. Here we screened for mutations the entire coding sequence of BRG1 (SMARCA4), which encodes the ATPase of the complex, in 59 lung cancer cell lines of the most common histopathological types. Mutations were detected in 24% of the cancer cell lines, many of them in cells commonly used for lung cancer research. All mutations were homozygous and most predicted truncated proteins. The alterations were significantly more frequent in the non-small-cell lung cancer (NSCLC) type (13/37, 35%) as compared to the small-cell lung cancer (SCLC) type (1/19, 5%) (P<0.05; Fisher's Exact test) and BRG1 was the fourth most frequently altered gene in NSCLC cell lines. BRG1 mutations coexisted with mutations/deletions at KRAS, LKB1, NRAS, P16, and P53. However, alterations at BRG1 always occurred in the absence of MYC amplification, suggesting a common role in lung cancer development. In conclusion, our data strongly support that BRG1 is a bona fide tumor suppressor and a major factor in lung tumorigenesis.
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PMID:Frequent BRG1/SMARCA4-inactivating mutations in human lung cancer cell lines. 1838 74

The members of the tumor suppressor p53 family are under tight regulation by distinct ubiquitin-protein isopeptide (E3) ligases. The level of p73 is regulated by the E3 ligase Itch. Itch levels are sharply reduced in response to DNA damage with concomitant p73 accumulation and activation. The mechanism of controlling Itch level is not known. We show that the Itch promoter is a target of the transcription activator Runx. Yes-associated protein (Yap1) is a shared transcription co-activator of Runx and p73. Under normal conditions, the Runx-Yap1 complex binds the Itch promoter and supports its transcription and p73 degradation. In response to DNA damage, Yap1 is phosphorylated by c-Abl at the position Tyr-357. The modified Yap1 does not co-activate Runx in supporting Itch transcription. The subsequent reduction in the Itch level gives rise to p73 accumulation. These results demonstrate how Yap1 supports degradation of p73 via Runx and how it plays an opposite role in response to DNA damage.
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PMID:A regulatory circuit controlling Itch-mediated p73 degradation by Runx. 1870 49

The MDM2 oncoprotein is a key negative regulator of the tumor suppressor p53. A functional MDM2 single nucleotide polymorphism (SNP309) in the promoter region increases the affinity of transcription activator Sp1 for the MDM2 gene promoter, resulting in higher expression of MDM2 and thus inhibition of p53 transcriptional activity. UV-induced p53 activation promotes cutaneous transient pigmentation, and the common p53 Arg72Pro polymorphism alters the protein's transcriptional activity. We evaluated the effect of MDM2 SNP309 and its interaction with the p53 Arg72Pro polymorphism on pigmentary phenotypes and skin cancer risk in a nested case-control study within the Nurses' Health Study (NHS) among 219 melanoma cases, 286 squamous cell carcinoma (SCC) cases, 300 basal cell carcinoma (BCC) cases, and 873 controls, and among controls from other studies. We found that the G allele of the MDM2 SNP309 was inversely associated with the presence/absence of moles on the arm among 3,207 women pooled from controls of three nested case-control studies within the NHS. Compared with the MDM2 SNP309 T/T genotype, adjusted odds ratios (ORs) of having moles on the arms for T/G and G/G genotypes were 0.92 (95% confidence interval (CI), 0.78-1.08) and 0.68 (95% CI, 0.53-0.87), respectively (p, trend, 0.005). We observed suggestive evidence of the association between the carriage of the MDM2 SNP309 G allele and childhood tanning tendency (adjusted OR, 1.30; 95% CI, 1.01-1.68). No significant associations were found between the MDM2 SNP309 and any of the three types of skin cancer. For SCC, the trend of increased risk across the three genotypes of MDM2 was stronger among p53 Pro carriers (p, trend, 0.05) than p53 Arg/Arg wild-type group (p, trend, 0.99; p, interaction, 0.07). These results provide evidence for the potential involvement of MDM2 SNP309 in pigmentary traits.
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PMID:A functional SNP in the MDM2 promoter, pigmentary phenotypes, and risk of skin cancer. 1881 47

Although SWI/SNF chromatin remodeling complexes play important roles in transcription, recent studies suggest that they also participate directly in DNA repair. In yeast, SWI/SNF and related RSC complexes have been shown to be recruited to the sites of DNA double strand breaks (DSBs) to facilitate DNA repair. We recently have shown that mammalian SWI/SNF complexes contribute to DBS repair by direct mechanisms of stimulating the phosphorylation of histone H2AX at DSB-surrounding chromatin. Here we investigated the role of mammalian SWI/SNF complexes in cell survival after DNA damage. When SWI/SNF was inactivated by means of dominant negativity or its catalytic subunit BRG1 was knockdowned by small interfering RNA, cells became highly susceptible to DNA damage-induced apoptosis. SWI/SNF inactivation had no effect on the activation and establishment of G2/M DNA damage checkpoint. However, SWI/SNF-defective cells could not sustain the G2/M checkpoint long enough to survive DNA damage, and rather underwent apoptosis before entering mitosis. We also found that, although the basal state and DNA damage-triggered activation of p53 were normal, the kinetics of p53 downregulation was significantly delayed in SWI/SNF-defective cells. Finally, the sustained p53 activation in SWI/SNF-defective cells was accompanied by accumulation of unrepaired DSBs owing to inefficient DNA repair. These results suggest that mammalian SWI/SNF complexes prevent DNA damage-induced apoptosis in part by facilitating efficient repair and thereby ensuring timely elimination of unrepaired DSBs that could otherwise lead to excessive prolongation of p53 activation.
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PMID:Mammalian SWI/SNF chromatin remodeling complexes are required to prevent apoptosis after DNA damage. 1882 92

A highly-parallel yeast functional assay, capable of screening approximately 100-1,000 mutants in parallel and designed to screen the activity of transcription activator proteins, was utilized to functionally characterize tetramerization domain mutants of the human p53 transcription factor and tumor suppressor protein. A library containing each of the 19 possible single amino acid substitutions (57 mutants) at three positions in the tetramerization domain of the human p53 protein, was functionally screened in Saccharomyces cerevisiae. Amino acids Leu330 and Ile332, whose side chains form a portion of a hydrophobic pocket that stabilizes the active p53 tetramer, were found to tolerate most hydrophobic amino acid substitutions while hydrophilic substitutions resulted in the inactivation of the protein. Amino acid Gln331 tolerated essentially all mutations. Importantly, highly parallel mutagenesis and cloning techniques were utilized which, in conjunction with recently reported highly parallel DNA sequencing methods, would be capable of increasing throughput an additional 2-3 orders of magnitude.
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PMID:Parallel analysis of tetramerization domain mutants of the human p53 protein using PCR colonies. 1892 36


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