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

The tumor suppressor protein p53 is a metal-binding transcription factor whose conformation and function are altered by mutation in cancers. Using murine p53 translated in vitro, we report here that concentrations of copper within the physiological range (< 30 microM) alter the conformation of wild-type p53 and inhibit sequence-specific DNA-binding. Direct binding of copper to p53 in the form of Cu(I) was demonstrated by Electron Spin Resonance using a purified recombinant protein containing residues 1-343 of murine wild-type p53 fused to E. coli maltose binding protein. Moreover, protection against the effect of Cu(II) sulfate was achieved by the Cu(I)-specific chelator bathocuproinedisulfonic acid but not by scavengers of reactive oxygen species, suggesting that alteration of p53 by copper depends upon a Cu(II)/Cu(I) redox mechanism, but does not require the production of reactive oxygen species. Thus copper at physiological concentrations can interact with wild-type p53 and affect its DNA-binding capacity.
 ...
PMID:Modulation by copper of p53 conformation and sequence-specific DNA binding: role for Cu(II)/Cu(I) redox mechanism. 782 76

A plasmid carrying the 5' flanking region of the mouse proliferating-cell-nuclear-antigen (PCNA) gene or DNA polymerase beta gene was fused with the chloramphenicol acetyltransferase (CAT) gene, then cotransfected into mouse N18TG2 cells with the expression plasmid for the p53 gene. Expression of the wild-type p53 repressed the CAT expression directed by the PCNA gene promoter, while it had little effect on the DNA polymerase beta gene promoter. RNase protection analysis revealed that the repression of the PCNA gene promoter by p53 was at the transcription step. Analysis with various deletion mutants in the PCNA gene promoter revealed that a specific sequence is not required for the repression, suggesting that p53 represses the PCNA gene promoter by interacting with some components of the basic transcription machinery. By analysis with various deletion mutants in the DNA polymerase beta gene promoter, we identified the unique 10-bp palindromic sequence (-24 to -15), in the presence of which p53 was not able to repress the promoter activity. This sequence conferred resistance to p53 repression onto the PCNA gene promoter, when it was placed 21-bp upstream from the transcription-initiation site.
 ...
PMID:Differential effect of p53 on the promoters of mouse DNA polymerase beta gene and proliferating-cell-nuclear-antigen gene. 790 18

An oncogene product, p53, interacts with a simian virus 40-encoded T-antigen, which is an initiation protein for the viral DNA replication and also works as DNA helicase during elongation. Here we examine the interaction of p53 with cellular DNA helicase. A recombinant human wild type p53 fused with glutathione S-transferase was immobilized on glutathione-agarose as a ligand for affinity column. Hela cell extract was applied to the p53 column and the adsorbed proteins were eluted with buffers containing salt, 50% ethylene glycol, and glutathione. The ethylene glycol fraction contained a number of p53 binding proteins, and this fraction showed a DNA helicase activity measured by the displacement of DNA fragment from partially duplexed M13 DNA. The DNA helicase translocated in a 5'-to-3' direction on the single-stranded DNA using ATP as an energy source. The glutathione fraction that contained the p53 glutathione S-transferase fused protein also showed the same activity. The corresponding fractions from a control column carrying glutathione S-transferase showed only a trace amount of activity of DNA helicase. Therefore, the binding may be specific. Furthermore, an anti-p53 antibody column retained a p53-DNA helicase complex when the crude extracts of human placenta and of osteosarcoma cells were applied. These results indicate that p53 physically interacts with DNA helicase in vitro as well as in vivo.
 ...
PMID:Anti-oncogene product p53 binds DNA helicase. 795 81

Transgenic mice carrying the SV40 early region fused to the Drosophila hsp70 promoter developed smooth muscle and bone neoplasms. The smooth muscle tumors appeared in aged mice and were preferentially located on the muzzle or eyelids. Multiple neoplasms were often present and each appeared to be an independent proliferation. In contrast, the bone tumors typically developed in the petrous ridge and had all the features of osteogenic sarcomas, displaying distant metastasis and invasion of the brain. Cells in both types of tumors exhibited nuclear expression of SV40 T antigen. Mice homozygous for the transgene had a shorter latency for appearance of smooth muscle tumors and developed osteosarcomas more frequently than hemizygous mice. This model system implicates the cellular T antigen-binding proteins, such as Rb and p53, in the pathogenesis of bone and soft tissue neoplasms in mice.
 ...
PMID:Smooth muscle and bone neoplasms in transgenic mice expressing SV40 T antigen. 808 93

Mutations within a conserved "conformational" domain of the p53 protein have frequently been observed in a wide variety of human cancers. A hybrid protein containing the wild-type conformational domain of p53 fused to protein A bound to calf thymus DNA and a specific p53 DNA-binding motif. Hybrid proteins containing mutations in p53 bound to DNA less efficiently than wild-type hybrid protein. In addition, competition experiments showed that mutated p53 DNA-binding motif failed to interact with p53 hybrid proteins. The DNA-binding activity of wild-type p53 hybrid protein was inhibited by the metal chelator 1,10-phenanthroline. These results demonstrate that DNA-binding activity resides in the conformational domain of p53, providing a structural model for disruption of DNA binding by mutation. Furthermore, metal ions may regulate binding of p53 to DNA by modulating its conformation.
 ...
PMID:Sequence-specific interaction of a conformational domain of p53 with DNA. 822 71

The genes regulated by p53, as well as the factors modulating its function, need to be identified before the mechanism of action of p53 in control of cell growth can be adequately understood. Binding of the SV40 large T-antigen protein to an evolutionally conserved (conformational) domain of p53 inhibits p53's DNA-binding and transcription activation activities. Cellular proteins might also bind to this same region of p53 to regulate its function. A hybrid protein composed of protein A fused to the conformational domain (amino acids 115-295) of p53 was expressed in Escherichia coli and used as an affinity probe for binding proteins in detergent lysates of non-small cell lung carcinoma (NSCLC) cells. The wild-type p53 hybrid protein associated with several major proteins of molecular weights 45 K, 56 K, and 70 K, as well as other minor species ranging in molecular weight from 30 K to 90 K. These proteins bound specifically to the p53 sequence of the hybrid protein. Protein A did not associate with these proteins and the two p53 hybrid proteins containing missense mutations at codons 273 and 175 exhibited a 40-80% weaker association. In addition, T antigen competed with the cellular proteins for binding to the conformational domain. The conditions of cell growth had a profound effect on the expression of the p53 binding proteins. Considerably more p53 binding proteins were expressed in actively growing cells than in cultures maintained under conditions for slow growth. Quantitative differences in expression of p53-binding proteins were observed among different NSCLC cell lines. The expression of p53-binding proteins was not restricted to NSCLC cell lines; detergent extracts of an osteosarcoma cell line yielded similar p53-binding proteins.
 ...
PMID:Binding of cellular proteins to a conformational domain of tumor suppressor protein p53. 824 46

The tumour-suppressor gene p53 is inactivated in most human malignancies either by missense mutations or by binding to oncogenic proteins. In human soft tissue sarcomas, inactivation apparently results from MDM2 gene amplification. MDM2 is an oncogene product that may function by binding to p53 and inhibiting its ability to activate transcription. Here we show that, when expressed in Saccharomyces cerevisiae, human MDM2 inhibits human p53's ability to stimulate transcription by binding to a region that nearly coincides with the p53 acidic activation domain. The isolated p53 activation domain fused to another DNA-binding protein is also inactivated by MDM2, confirming that MDM2 can inhibit p53 function by concealing the activation domain of p53 from the cellular transcription machinery.
 ...
PMID:Oncoprotein MDM2 conceals the activation domain of tumour suppressor p53. 847 25

Antioncogene product p53 is a transcriptional transactivator. To investigate how p53 stimulates transcription, we examined the interaction of p53 with general transcription factors in vitro. We found that p53 binds directly to the human TATA box-binding polypeptide (TBP). We also observed a direct interaction between p53 and purified holo-TFIID, a complex composed of TBP and a group of TBP-associated polypeptides known as TAFs. The p53 binding domain on TBP was mapped to the conserved region of TBP, including residues 220 to 271. The TBP binding domain on p53 was mapped to the p53 activation domain between residues 20 and 57. To analyze the significance of the p53-TBP interaction in p53 transactivation, we compared the ability of Gal4-p53 fusion proteins to bind to TBP in vitro and to activate transcription in transient transfection assays. Fusion proteins which bound to TBP activated transcription, and those that did not bind to TBP did not activate transcription to a detectable level, suggesting that a direct interaction between TBP and p53 is required for p53 transactivation. We also found that inclusion of residues 93 to 160 of p53 in a Gal4-p53 fusion repressed transcriptional activation 100-fold. Consequently, this region of p53 inhibits transcriptional activation by the minimal p53 activation domain. Highest levels of activation were observed with sequences 1 to 92 of p53 fused to Gal4, even though this construct bound to TBP in vitro with an affinity similar to that of other Gal4-p53 fusion proteins. We conclude that TBP binding is necessary for p53 transcriptional activation and that p53 sequences outside the TBP binding domain modulate the level of activation.
 ...
PMID:The p53 activation domain binds the TATA box-binding polypeptide in Holo-TFIID, and a neighboring p53 domain inhibits transcription. 849 52

We used a yeast-based genetic assay, the two-hybrid system, to characterize the domain of the tumor-suppressor p53 involved in oligomerization. This assay relies on the reconstitution of the function of a transcriptional activator, the yeast GAL4 protein, via the interaction of a protein fused to the DNA-binding domain of GAL4 with a protein fused to the transcriptional activation domain of GAL4. We show by a reconstruction experiment that this approach could detect the interaction of p53 deleted for its N-terminal activation domain with SV40 large T antigen. We then searched a library of human proteins present as activation domain hybrids for proteins that can interact with the hybrid of p53 with the DNA-binding domain. This search identified 36 plasmids containing the p53 gene, representing 10 different classes. These results provide an additional in vivo demonstration of p53 oligomerization. The smallest p53 fragment identified from screening the library contained only amino acids 331-393, indicating that this small C-terminal fragment is sufficient to mediate oligomerization. In addition, a mutant p53 protein could bind to the wild-type protein in this assay, providing support for the idea that mutant forms of p53 act in a dominant-negative manner through C-terminal oligomerization with the wild type.
 ...
PMID:Use of the two-hybrid system to identify the domain of p53 involved in oligomerization. 850 89

Molecular events associated with the transformation into blast crisis phase in Ph1-positive CML were analyzed in the present study. The 9;22 chromosomal translocation in CML generates the bcr/abl fused gene coding P210bcr/abl that has enhanced tyrosine kinase activity. In 55 CML cases, Southern and RT-PCR analysis revealed that breakpoints of the bcr gene on chromosome 22q11 were clustered in M-bcr, except for one case and no obvious difference was observed between chronic and crisis phases. However, blast crisis cells displayed enhanced the expression of bcr/abl mRNA, when compared with those in chronic phase cells. By DNA transfection and PCR analysis, the point-mutational activation of N-ras oncogene was rarely identified, and no point-mutational activation of fms gene was found in the crisis phase cases. On the other hand, 2 out of 13 crisis cases contained gross alteration of p53 anti-oncogene. Furthermore, all 4 myeloid crisis cases and K562 cells showed disappearance of the P53 transcript, and MC3 cells derived from a myeloid crisis case showed an aberrant transcript, whereas chronic phase cases, Ph1-positive ALL cell lines and lymphoid crisis cases including NALM-1 cells showed normal expression of the P53 gene. At present, the precise mechanism associated with the blastic trans-formation in CML remain to be determined. The present study suggested one possibility that a selective and progressive process of Ph1 clone with high expression of the bcr/abl gene may be involved with the transformation into non-lymphoid crisis phases from chronic phases. In addition, this progression may be accelerated by the alteration of p53 anti-oncogene, or/and rarely by the point-mutational activation of ras oncogene family.
 ...
PMID:[Molecular analysis of transformation into blast crisis in chronic myelogenous leukemia]. 850 66


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>