Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:B6E4X6 (mutant p53)
 3,342 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Wild-type p53 is a short-lived protein which turns over very rapidly via selective proteolysis in the ubiquitin-proteasome pathway. Most p53 mutations, however, encode for protein products which display markedly increased intracellular levels and are associated with positive tumor-promoting activity. The mechanism by which mutation leads to impairment of ubiquitination and proteasome-mediated degradation is unknown, but it has been noted that many transforming p53 mutants are found in stable physical association with molecular chaperones of the hsp70 class. To explore a possible role for aberrant chaperone interactions in mediating the altered function of mutant p53 and its intracellular accumulation, we examined the chaperone proteins which physically associate with a temperature-sensitive murine p53 mutant. In lysate prepared from A1-5 cells grown under mutant temperature conditions, hsp70 coprecipitated with p53Val135 as previously reported by others, but in addition, other well-recognized elements of the cellular chaperone machinery, including hsp90, cyclophilin 40, and p23, were detected. Under temperature conditions favoring wild-type p53 conformation, the coprecipitation of chaperone proteins with p53 was lost in conjunction with the restoration of its transcriptional activating activity. Chaperone interactions similar to those demonstrated in A1-5 cells under mutant conditions were also detected in human breast cancer cells expressing two different hot-spot mutations. To examine the effect of directly disrupting chaperone interactions with mutant p53, we made use of geldanamycin (GA), a selective hsp90-binding agent which has been shown to alter the chaperone associations regulating the function of unliganded steroid receptors. GA treatment of cells altered heteroprotein complex formation with several different mutant p53 species. It increased p53 turnover and resulted in nuclear translocation of the protein in A1-5 cells. GA did not, however, appear to restore wild-type transcriptional activating activity to mutant p53 proteins in either A1-5 cells or human breast cancer cell lines.
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PMID:The physical association of multiple molecular chaperone proteins with mutant p53 is altered by geldanamycin, an hsp90-binding agent. 948 68

Exposure of mammalian cells to ultraviolet (UV) light and other DNA-damaging agents triggers the UV response which is characterized by induction of a large number of genes including c-fos, c-jun, and the genes for DNA repair enzymes and cell-cycle regulatory proteins such as p21 WAF1 and p53. Upon DNA damage, the p53 tumor suppressor protein transmits signals to restrict cell-cycle progression, thereby allowing time for DNA repair to occur. Cells also respond to genotoxic stress by activation of the jun N-terminal kinase (JNK)/stress-activated protein kinase pathway. In this report we investigated the effects of modulation of the level of wild-type and mutant p53 protein on basal and UV-inducible JNK activity. We used the A1-5 rat fibroblast cell line, which contains a p53 gene coding for a temperature-sensitive p53 protein, which allows us to regulate the relative level of wild-type and mutant p53 protein produced in a cell. We measured the relative levels of JNK activity in sham-irradiated and UV-irradiated cells by using the immune complex kinase assay and then computed the fold induction of JNK after UV exposure. We demonstrated that cells expressing p53 protein in the wild-type conformation (when grown at 32 degrees C) exhibited a very low level of JNK activity that was induced 14- to 16-fold by UVC irradiation. When cells were grown at 37 degrees C or 39 degrees C to express predominantly mutant p53 protein, basal JNK activity was significantly higher than at 32 degrees C. UVC irradiation of cells expressing mutant p53 protein resulted in JNK activation, although the overall fold-induction was only two-fold because JNK1 activity was already high in the sham-treated controls. UVB irradiation also induced JNK1 activity, although we again observed a relatively high level of basal JNK activity in sham-irradiated cells expressing mutant p53 protein compared with cells expressing wild-type p53. Control experiments confirmed that JNK1 basal activity was not affected by temperature alone. Western blot analysis of cell extracts indicated that expression of p21 WAF protein was significantly higher in cells expressing wild-type p53 protein and was associated with low basal levels of JNK1 activity. In contrast, cells expressing mutant p53 protein and very low levels of p21 WAF1 protein were found to have a higher level of basal JNK1 activity. We also observed a reduced ability to induce JNK1 after UV irradiation of several other cell lines with p53-mutant or p53-null genotypes. Our results provide evidence for a novel connection between p53 status and the basal level of JNK1, a critical enzyme in the stress-activated protein kinase family. In addition, these studies suggest that the presence of mutant p53 protein in a cell not only affects basal activity of JNK1 but also affects the ability of a cell to respond to UV-induced stress by transmitting signals via induction or activation of the JNK1 cascade.
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PMID:Mutational status of the p53 gene modulates the basal level of jun N-terminal kinase and its inducibility by ultraviolet irradiation in A1-5 rat fibroblasts. 1044 33

Exposure of mammalian cells to genotoxic stress results in activation of the c-jun amino-terminal kinase (JNK)-stress-activated protein kinase (SAPK) pathway and induction of DNA repair enzymes and cell cycle-regulatory proteins such as p53 and p21waf1. The p53 tumor suppressor protein transmits signals that activate p21waf1 gene expression. The p21waf1 protein then restricts cell-cycle progression, thereby allowing time for DNA repair to occur. In this study, we investigated the effects of modulation of the level of wild-type and mutant p53 protein on basal JNK1 activity in the A1-5 rat fibroblast cell line. This cell line contains a p53 gene coding for a temperature-sensitive p53 protein, which allows us to regulate the relative level of wild-type and mutant p53 protein produced in cells. Using the immune complex kinase assay to measure JNK1 activity, we demonstrated that cells expressing the wild-type-conformation p53 protein (when grown at 32.5 degrees C) exhibited a very low level of JNK1 activity. When cells were grown at 37 degrees C or 39 degrees C to express predominantly mutant p53 protein, basal level of JNK1 activity was significantly higher than at 32.5 degrees C. We also demonstrated protein-protein interactions between the p53, p21waf1, and JNK1 proteins in this cell line. Both wild-type p53 protein (expressed at 32.5 degrees C) and mutant p53(val135) protein (expressed at 37 degrees C and 39 degrees C) were present in immunocomplexes of JNK1 protein. Under conditions where wild-type p53 protein was present to induce p21waf1 expression (at 32.5 degrees C), a higher level of p21waf1 protein was also detected in the JNK1 immunocomplexes than in those at 37 degrees C and 39 degrees C. We next investigated the effect that co-association of p53 protein and p21waf1 protein would have on JNK1 activity. We measured basal levels of JNK1 activity in cells expressing wild-type p53 and p21waf1, or in p21waf1-null cells, and demonstrated that cells expressing both p53 and p21waf1 proteins exhibited an approximately threefold lower basal level of JNK1 activity when compared with p21waf1-null cells. To confirm that p21waf1 protein expression in cells resulted in reduced JNK1 activity, we transfected p21waf1-/- cells with a p21waf1 expression vector. We observed that JNK1 activity was inhibited after exogenous p21waf1 protein was expressed in these cells. Our results provide evidence for modulation of the JNK1 pathway by p53 and p21waf1 proteins and support the hypothesis that modulation of JNK1 activity occurred through protein-protein interactions between JNK1, p53, and p21waf1 proteins.
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PMID:Association of JNK1 with p21waf1 and p53: modulation of JNK1 activity. 1250 78