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)

We have identified the phosphorylation sites in monkey p53 as well as specific changes in the phosphorylation state of free and complexed forms of simian virus 40 (SV40) large T antigen (T) and monkey p53 isolate from SV40 lytically infected CV1 cells. Phosphopeptide analyses of free T and p53 (To and p53o) and complexed T and p53 (T+ and p53+) fractions indicated several quantitative increases in the specific phosphorylation of complexed forms of both proteins. The N terminus of monkey p53+ is phosphorylated at Ser-9, Ser-15, Ser-20, either Ser-33 or Ser-37, and at least one of Ser-90 to Ser-99. The C-terminal sites are Ser-315 and Ser-392. On comparing p53+ with p53o, we found that labeling of the two N-terminal phosphotryptic peptides encompassing residues 1 to 20 and 33 to 101 was increased fivefold and that Ser-315 was sevenfold more labeled than was Ser-392. When T+ was compared with To, the N-terminal peptide containing phosphorylation sites Ser-106 through Thr-124 was twofold more labeled, the peptide containing Ser-657 through Ser-679 was sixfold more labeled and contained up to four phosphorylated serine residues, and Ser-639 and Thr-701 appeared unchanged. Overall, T+ molecules appeared to contain 3.5 mol more of labeled phosphate than did To, with the N-terminal peptide appearing fully phosphorylated. The phosphopeptide patterns obtained for lytic T+ and To fractions were nearly identical to those found for wild-type SV40 T (stably complexed with mouse p53) and mutant 5080 T (defective for p53 binding) expressed in transformed C3H10T1/2 cells (L. Tack, C. Cartwright, J. Wright, A. Srinivasan, W. Eckhart, K. Peden, and J. Pipas, J. Virol. 63:3362-3367, 1989). These results indicate that increases in specific phosphorylation sites in both T+ and p53+ correlate with the association of T with p53. The enhanced phosphorylation state may be a consequence of complex formation between T and p53 or reflect an increased affinity of p53 for highly phosphorylated forms of T.
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PMID:Altered phosphorylation of free and bound forms of monkey p53 and simian virus 40 large T antigen during lytic infection. 131 Jul 51

A rabbit antiserum was prepared against the C-terminal peptide of 21 amino acids from the human heat shock protein hsp70. These antibodies were shown to be specific for this highly inducible heat shock protein (72 kilodaltons [kDa] in rat cells), and for a moderately inducible, constitutively expressed heat shock protein, hsc70 (74 kDa). In six independently derived rat cell lines transformed by a murine cDNA-genomic hybrid clone of p53 plus an activated Ha-ras gene, elevated levels of p53 were detected by immunoprecipitation by using murine-specific anti-p53 monoclonal antibodies. In all cases, the hsc70, but not the hsp70, protein was coimmunoprecipitated with the murine p53 protein. Similarly, antiserum to heat shock protein coimmunoprecipitated p53. Western blot (immunoblot) analysis demonstrated that the hsc70 and p53 proteins did not share detectable antigenic epitopes. The results provide clear immunological evidence for the specific association of a single heat shock protein, hsc70, with p53 in p53-plus-ras-transformed cell lines. A p53 cDNA clone, p11-4, failed to produce clonable cell lines from foci of primary rat cells transfected with p11-4 plus Ha-ras. A mutant p53 cDNA clone derived from p11-4, SVKH215, yielded a 2- to 35-fold increase in the number of foci produced after transfection of rat cells with SVKH215 plus Ha-ras. When cloned, 87.5% of these foci produced transformed cell lines. SVKH215 encodes a mutant p53 protein that binds preferentially to the heat shock proteins of 70 kDa compared with binding by the parental p11-4 p53 gene product. These data suggest that the p53-hsc70 protein complex could have functional significance in these transformed cells.
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PMID:Immunological evidence for the association of p53 with a heat shock protein, hsc70, in p53-plus-ras-transformed cell lines. 331 6

The expression of the 7B2 protein, secreted from a variety of neural and endocrine tissues, increases dramatically in specific neuroendocrine tumors. We have recently shown that human 7B2 can act as a molecular chaperone in the deaggregation of proteins in vitro. In order to identify polypeptides which might bind 7B2 in vivo, the yeast two-hybrid system was employed. Surprisingly, mere covalent linkage of 7B2 to the DNA-binding domains of two yeast transcription activators, Ace1 and Gal4, activates transcription from the ACE1 and GAL4 operon. 7B2's ability to activate nuclear transcription surpasses that of Ace1 and compares favourably with the strong activation domain of the tumor suppressor protein, p53. Our results suggest that 7B2 must possess an activating sequence, a domain which defines all transcriptional activator proteins. Like the acidic activation domains of some transcriptional activators, 7B2 also binds the yeast TATA-box binding protein, an essential polypeptide in the basic transcription machinery. Deletion analysis of the gene encoding 7B2 reveals two independent transcriptional activating sequences in the 185 amino acid protein. It is therefore conceivable that 7B2 not only has a functional role in the secretory pathway but also in the nucleus. Moreover, these findings raise an intriguing question regarding the activation domains of 7B2 and their possible link to 7B2's oncogenic potential.
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PMID:The neuroendocrine protein 7B2 contains unusually potent transcriptional activating sequences. 748 73

The neuroendocrine protein 7B2 prevents premature activation of PC2, an enzyme involved in the processing of prohormones in the secretory pathway. We inquired if this chaperone-like function encompasses a broader role for 7B2 in the folding of hormone-like proteins. As a test, the fate of misfolded human insulin-like growth factor-1 (IGF1) was assessed, in the presence and absence of 7B2. Most of the recombinant IGF1 molecules, secreted from yeast, are a conglomeration of inactive multimers which are either disulfide-linked or mere physical aggregates. We find that yeast-produced 7B2 influences the in vitro conversion of inactive molecules into active monomers. However, the amounts of disulfide-linked dimers remain unaffected during this conversion. Interestingly, both 7B2 and the molecular chaperone DnaK interact with IGF1 in the yeast two-hybrid system. Like DnaK, 7B2 also binds the tumor suppressor protein p53. Binding of DnaK to exposed epitopes of aggregated proteins is known to be a prerequisite for deaggregation. It is conceivable that 7B2 participates in an analogous manner in the dissociation of non-covalently linked multimers of IGF1. Our results indicate that 7B2 might find an application in the deaggregation of potentially useful therapeutic proteins.
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PMID:The neuroendocrine protein 7B2 acts as a molecular chaperone in the in vitro folding of human insulin-like growth factor-1 secreted from yeast. 779 52

The tumor suppressor p53 has two DNA binding domains: a central sequence-specific domain and a C-terminal sequence-independent domain. Here, we show that binding of large but not small DNAs by the C terminus of p53 negatively regulates sequence-specific DNA binding by the central domain. Four previously described mechanisms for activation of specific DNA binding operate by blocking negative regulation. Deletion of the C terminus of p53 activates specific DNA binding only in the presence of large DNA. Three activator molecules (a small nucleic acid, a monoclonal antibody against the p53 C terminus, and a C-terminal peptide of p53) stimulate sequence-specific DNA binding only in the presence of both large DNA and p53 with an intact C terminus. Our findings argue that interactions of the C terminus of p53 with genomic DNA in vivo would prevent p53 binding to specific promoters and that cellular mechanisms to block C-terminal DNA binding would be required.
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PMID:Reciprocal interference between the sequence-specific core and nonspecific C-terminal DNA binding domains of p53: implications for regulation. 934 86

A synthetic 22-mer peptide (peptide 46) derived from the p53 C-terminal domain can restore the growth suppressor function of mutant p53 proteins in human tumor cells (G. Selivanova et al., Nat. Med. 3:632-638, 1997). Here we demonstrate that peptide 46 binds mutant p53. Peptide 46 binding sites were found within both the core and C-terminal domains of p53. Lys residues within the peptide were critical for both p53 activation and core domain binding. The sequence-specific DNA binding of isolated tumor-derived mutant p53 core domains was restored by a C-terminal polypeptide. Our results indicate that C-terminal peptide binding to the core domain activates p53 through displacement of the negative regulatory C-terminal domain. Furthermore, stabilization of the core domain structure and/or establishment of novel DNA contacts may contribute to the reactivation of mutant p53. These findings should facilitate the design of p53-reactivating drugs for cancer therapy.
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PMID:Reactivation of mutant p53 through interaction of a C-terminal peptide with the core domain. 1020 63

A p53-derived C-terminal peptide induced rapid apoptosis in breast cancer cell lines carrying endogenous p53 mutations or overexpressed wild-type (wt) p53 but was not toxic to nonmalignant human cell lines containing wt p53. Apoptosis occurred through a Fas/APO-1 signaling pathway involving increased extracellular levels of Fas/FasL in the absence of protein synthesis, as well as activation of a Fas/APO-1-specific protease, FLICE. The peptide activity was p53-dependent, and it had no effect in three tumor cell lines with null p53. Furthermore, the C-terminal peptide bound to p53 protein in cell extracts. Thus, p53-dependent, Fas/APO-1 mediated apoptosis can be induced in breast cancer cells with mutant p53 similar to the recently described Fas/APO-1 induced apoptosis by wt p53. However, mutant p53 without p53 peptide does not induce a Fas/APO-1 activation or apoptosis. Docking of the computed low energy conformations for the C-terminal peptide with those for a recently defined proline-rich regulatory region from the N-terminal domain of p53 suggests a unique low energy complex between the two peptide domains. The selective and rapid induction of apoptosis in cancer cells carrying p53 abnormalities may lead to a novel therapeutic modality.
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PMID:Conformational and molecular basis for induction of apoptosis by a p53 C-terminal peptide in human cancer cells. 1057 67

The p53 tumor suppressor protein is stabilized in response to ionizing radiation and accumulates in the nucleus. Stabilization is thought to involve disruption of the interaction between the p53 protein and Mdm2, which targets p53 for degradation. Here we show that the direct association between a p53 N-terminal peptide and Mdm2 is disrupted by phosphorylation of the peptide on Thr(18) but not by phosphorylation at other N-terminal sites, including Ser(15) and Ser(37). Thr(18) was phosphorylated in vitro by casein kinase (CK1); this process required the prior phosphorylation of Ser(15). Thr(18) was phosphorylated in vivo in response to DNA damage, and such phosphorylation required Ser(15). Our results suggest that stabilization of p53 after ionizing radiation may result, in part, from an inhibition of Mdm2 binding through a phosphorylation-phosphorylation cascade involving DNA damage-activated phosphorylation of p53 Ser(15) followed by phosphorylation of Thr(18).
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PMID:Damage-mediated phosphorylation of human p53 threonine 18 through a cascade mediated by a casein 1-like kinase. Effect on Mdm2 binding. 1073 67

Upon exposure to DNA-damaging agents, the p53 tumor suppressor protein is stabilized and activated, leading to cell cycle arrest, DNA repair, or apoptosis. One of the major factors that regulates the level and the transcriptional activity of p53 is the hdm2 oncoprotein. hdm2 binds to the N-terminal transactivation domain of p53 to block the transcriptional activity of p53 directly. hdm2 also functions as the E3 ligase that ubiquitinates p53 for proteasome degradation. Fluorescence anisotropy was employed to measure directly the binding of hdm2(1-126) to a p53 N-terminal peptide labeled with Oregon Green (an analogue of fluorescein). Phosphorylation of Ser15 and Ser2O did not affect the binding of the p53 peptide to hdm2. Thrl8 phosphorylation, on the other hand, reduced the binding by at least 20-fold. This suggests that phosphorylation of Thr18 could be a regulatory mechanism that disrupts the hdm2-p53 complex, thus activating p53 in response to DNA damage. The effect of p53 peptide length on binding to hdm2 was also measured quantitatively. Interestingly, p53(18-26) exhibits 10-fold higher affinity to hdm2 than do longer peptides (20- or 35-mer). This result may reflect a strong entropic barrier to binding for the longer peptides.
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PMID:Thermodynamics of p53 binding to hdm2(1-126): effects of phosphorylation and p53 peptide length. 1103 16

A physical and functional interaction between the Ca(2+)-binding protein Mts1 (S100A4) and the tumor suppressor p53 protein is shown here for the first time. We demonstrate that Mts1 binds to the extreme end of the C-terminal regulatory domain of p53 by several in vitro and in vivo approaches: co-immunoprecipitation, affinity chromatography, and far Western blot analysis. The Mts1 protein in vitro inhibits phosphorylation of the full-length p53 and its C-terminal peptide by protein kinase C but not by casein kinase II. The Mts1 binding to p53 interferes with the DNA binding activity of p53 in vitro and reporter gene transactivation in vivo, and this has a regulatory function. A differential modulation of the p53 target gene (p21/WAF, bax, thrombospondin-1, and mdm-2) transcription was observed upon Mts1 induction in tet-inducible cell lines expressing wild type p53. Mts1 cooperates with wild type p53 in apoptosis induction. Our data imply that the ability of Mts1 to enhance p53-dependent apoptosis might accelerate the loss of wild type p53 function in tumors. In this way, Mts1 can contribute to the development of a more aggressive phenotype during tumor progression.
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PMID:Tumor suppressor p53 protein is a new target for the metastasis-associated Mts1/S100A4 protein: functional consequences of their interaction. 1127 47


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