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Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Antisera prepared against BALB/c Meth A sarcoma in syngeneic or compatible F1 mice recognize a protein with an apparent molecular weight of 53,000 in extracts of [35S]methionine-labeled transformed BALB/c cells. This component, designated p53, was not detected in normal adult mouse fibroblasts, lymphoid cells, or hematopoietic cells or in mouse embryo cells or 3T3 cells. An extensive variety of antisera, including alloantisera and heterologous antisera directed against structural antigens of murine leukemia viruses, was tested for reactivity with p53; other than Meth A antisera, only comparably prepared antisera against another BALB/c sarcoma, CMS4, had anti-p53 activity. All transformed mouse cells tested were found to express p53; these tests included chemically induced sarcomas, leukemias, spontaneously transformed fibroblasts, and cells transformed by simian virus 40 and murine sarcoma virus. The presence of p53 in tumors of no known viral etiology indicates coding by resident cellular genes; this does not exclude endogenous viruses as the source of coding sequences or the possibility that transforming viruses code directly for p53.
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PMID:Detection of a transformation-related antigen in chemically induced sarcomas and other transformed cells of the mouse. 22 23

Biologically active mutant p53 from Balb/c mouse tumor cells (Meth A) was analysed for its specific interaction with DNA. Restricted phage lambda DNA, representing DNA of high complexity with regard to sequence and secondary structure, was used to probe for such an activity in a target-bound DNA-binding assay, using doubly immunopurified p53. A single lambda DNA fragment was specifically retained with very high affinity (KD = 10(-10) M). Specific DNA binding was shown to be an intrinsic property of p53, as it could be blocked with p53-specific monoclonal antibodies PAb122 and PAb421. The characteristics of the DNA binding of p53 to this lambda DNA fragment, as well as the structural properties of this fragment, suggested the possibility that p53 might be able to interact with nuclear matrix attachment region (MAR) DNA. Indeed, established genomic MAR elements were specifically bound by Meth A p53, whereas no binding was observed to an AT-rich control DNA. The interaction of p53 with MAR elements in vitro is compatible with the idea that p53 in vivo is involved in the regulation of replication and/or expression of cellular DNA. Complex DNA interactions were not restricted to mutant p53 from Meth A cells. Mutant p53 of a different conformational phenotype (PAb246+ 'wild-type' as opposed to PAb246- 'mutant' for p53 from Meth A cells) from minimally transformed T3T3 cells, as well as genotypic wild-type p53 expressed by a recombinant baculovirus in insect cells, exhibited similar DNA-binding properties.
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PMID:Specific and complex interactions of murine p53 with DNA. 140 33

In order to obtain insight into the parameters determining the subcellular localization of mutant and wild-type forms of p53, we analysed the subcellular distribution of p53 in four Balb/c mouse-derived cell lines ranging in their cellular phenotypes from normal (3T3), via minimal transformant (T3T3), to maximally transformed (3T3tx, Meth A). Epitope mapping showed the p53 proteins in 3T3 and in T3T3 cells to be in a wild-type conformation, as they reacted with PAb246, whereas p53 in 3T3tx and in Meth A cells were PAb246 negative and thus displayed a mutant conformation. Despite its reactivity with PAb246, p53 in T3T3 cells had an extended half-life and accumulated to abnormally high levels. We show that the conformationally wild-type p53 in 3T3 and T3T3 cells predominantly localized to the cell nucleus, with about half of it being tightly associated with nuclear structures. In contrast, approximately 60% of mutant p53 in 3T3tx and Meth A cells localized to the cytoplasm, the rest residing in the cell nucleus; all the nuclear p53 in these cells appeared to be structurally bound. The cytoplasmic location of mutant p53 in 3T3tx and Meth A cells was not seen by immunofluorescence microscopic analysis, and required cell fractionation for its detection. Both cytoplasmic and nuclear p53 of the mutant phenotype bound to hsc proteins with a similar stoichiometry, suggesting that hsc binding is not directly related to the subcellular distribution of these proteins. We suggest that the conformational phenotype of p53 is a major determinant of its subcellular location.
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PMID:Correlation between the conformational phenotype of p53 and its subcellular location. 162 May 50

In addition to controlling the transition of resting normal cells from the G0-state of the cell cycle into S-phase, expression of the cellular protein p53 also seems to be necessary for the proliferation of cycling normal cells in an as yet undefined manner. To further elaborate the role of p53 in growing cells, we analysed p53 expression and its regulation in cells going into, and after release from, growth arrest at the restriction point (R-point) in the G1-phase of the cell cycle, induced by isoleucine depletion. Since growth arrest at the R-point is subject to internal control mechanisms of the cell cycle, this approach allowed us to include in our analyses normal Balb/c 3T3 fibroblasts, as well as cells of the chemically induced Balb/c fibrosarcoma cell line Meth A, expressing mutated p53. Isoleucine depletion induced a viable growth arrest at the R-point in cells of both cell lines, marked by a synchronous shut-down of DNA synthesis when the cells went into growth arrest, and a synchronous resumption of DNA synthesis after a lag period of about 2-4 h when the cells were released from growth arrest, as well as a shift to a G1 DNA content at the R-point. p53 expression in both cell lines showed a phenotypically similar regulation, as its synthesis was specifically reduced at the R-point. At the molecular level, however, p53 expression in growth arrested 3T3 cells was controlled at the transcriptional/post-transcriptional level, whereas control in growth arrested Meth A cells seemed to be at the level of mRNA translation. After release from growth arrest, p53 synthesis in both types of cells was rapidly restored, preceding resumption of total protein synthesis, and exhibiting a p53-specific profile.
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PMID:Cell cycle control by p53 in normal (3T3) and chemically transformed (Meth A) mouse cells. I. Regulation of p53 expression. 226 35

To further characterize the role of p53 in growing normal Balb/c 3T3 fibroblasts, as well as of p53 in cells of the methylcholanthrene induced fibrosarcoma cell line Meth A, we analysed the effect of inhibition of p53 synthesis by microinjection of p53-specific monoclonal antibody PAb 122 into the nuclei of these cells after release from growth arrest induced by isoleucine starvation (see preceding paper [Steinmeyer et al., this issue] ). We show that microinjection of PAb 122, but not of control immunoglobulins, into the nuclei of both types of cells effectively blocked their re-entry into the S-phase of the cell cycle. Since isoleucine depletion of these cells was shown to lead to a growth arrest at the restriction point (R-point) in the G1-phase of the cell cycle, our results (i) define more precisely the role of p53 in growing cells as a protein controlling transition of the cells through this restriction point, and (ii) demonstrate that mutated p53 in Meth A cells still is functional with regard to cell cycle control at this restriction point. We suggest that p53 acts as a 'gate-keeping' protein at restriction points in the cell cycle, exerting a positive effect on the transition of cells through the cell cycle.
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PMID:Cell cycle control of p53 in normal (3T3) and chemically transformed (Meth A) mouse cells. II. Requirement for cell cycle progression. 226 36

The 11-4 p53 cDNA clone failed to transform primary rat fibroblasts when cotransfected with the ras oncogene. Two linker insertion mutations at amino acid 158 or 215 (of 390 amino acids) activated this p53 cDNA for transformation with ras. These mutant cDNAs produced a p53 protein that lacked an epitope, recognized by monoclonal antibody PAb246 (localized at amino acids 88 to 110 in the protein) and preferentially bound to a heat shock protein, hsc70. In rat cells transformed by a genomic p53 clone plus ras, two populations of p53 proteins were detected, PAb246+ and PAb246-, which did or did not bind to this monoclonal antibody, respectively. The PAb246- p53 preferentially associated with hsc70, and this protein had a half-life 4- to 20-fold longer than free p53 (PAb246+). These data suggest a possible functional role for hsc70 in the transformation process. cDNAs for p53 derived from methylcholanthrene-transformed cells transform rat cells in cooperation with the ras oncogene and produce a protein that bound with the heat shock proteins. Recombinant clones produced between a Meth A cDNA and 11-4 were tested for the ability to transform rat cells. A single amino acid substitution at residue 132 was sufficient to activate the 11-4 p53 cDNA for transformation. These studies have identified a region between amino acids 132 and 215 in the p53 protein which, when mutated, can activate the p53 cDNA. These results also call into question what the correct p53 wild-type sequence is and whether a wild-type p53 gene can transform cells in culture.
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PMID:Activating mutations for transformation by p53 produce a gene product that forms an hsc70-p53 complex with an altered half-life. 283 26

We analysed the in vitro binding of p53 from normal (3T3) and from chemically transformed (Meth A) Balb/c mouse cells to double-stranded (ds-) DNA and to single-stranded (ss-) DNA by DNA-cellulose chromatography. We confirm previous findings that p53 in cellular extracts exhibits ds-DNA-binding activity (Lane and Gannon, 1983). In addition, we demonstrate that such p53 also binds to ss-DNA. Analyses with immunopurified p53 protein provide evidence that this DNA-binding activity is intrinsic to p53. DNA binding of p53 could not be inhibited by a monoclonal antibody specific for the C-terminal region. An N-terminal deletion mutant of p53 (Rovinski et al., 1987) exhibited similar DNA-binding properties as wild-type p53, indicating that the N-terminus also is dispensable for DNA binding. We further show a close correlation between the DNA-binding activity of p53 from 3T3 cells and its association with nuclear substructures.
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PMID:DNA binding properties of murine p53. 297 67

Expression plasmids directing the synthesis of various forms of the p53 cellular tumor antigen were compared with respect to their biological activities. All plasmids encoding wild type p53, derived from two different cDNA libraries, had absolutely no detectable activity when assayed for transformation of primary rat embryo fibroblasts in collaboration with Ha-ras. In contrast, p53 variants carrying point mutations in the protein coding region exhibited at least some transforming activity. Most notably, this was true for both types of mutant p53 cDNA clones isolated from Meth A cells. The data indicate that these cells, derived from a chemically-induced tumor, carry two independently mutated p53 alleles, each encoding a transformationally activated protein. This may imply that the mutations in the p53 gene played a role in the development of the Meth A tumor. Finally, cells overexpressing a transfected mutant p53 exhibit a physical complex between this exogenous p53 and its endogenous counterpart, possibly resulting in the stabilization of the latter.
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PMID:Meth A fibrosarcoma cells express two transforming mutant p53 species. 306 Jul 94

BALB/c murine sarcoma Meth A is known to have three missense point mutations in p53. We previously reported that a nonamer peptide containing the codon 234 mutational product (designated 234CM) elicited 234CM-specific cytotoxic T cells and that immunization with 234CM in adjuvant before tumor challenge inhibited Meth A growth. Because interleukin 12 (IL-12) has been shown to have antitumor activity against established tumors and immuno-modulatory activities, we analyzed its effect on p53 peptide immunization and Meth A growth. Multiple injections of IL-12 alone (4 times a week for 2 weeks) caused regression of established Meth A sarcoma, and this effect was dose dependent. IL-12 treatment prior to Meth A challenge had little or no antitumor activity. To evaluate the effect of IL-12 on the generation of 234CM-specific cytotoxic T lymphocytes, spleen cells from BALB/c mice immunized with 234CM in adjuvant and injected with various doses of IL-12 were sensitized with 234CM in vitro. Multiple injections of 1 ng of IL-12 induced the highest cytotoxicity against target cells pulsed with 234CM. Higher doses of IL-12 suppressed 234CM-specific cytotoxic T-cell generation. Mice immunized with 234CM in QS-21 adjuvant and treated with 1 ng of IL-12 rejected established Meth A sarcoma. Mice comparably treated with 1 ng of IL-12 but immunized with 234CW peptide (the wild-type counterpart to 234CM) in QS-21 or with QS-21 alone showed progressive tumor growth.
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PMID:Influence of interleukin 12 on p53 peptide vaccination against established Meth A sarcoma. 789 50

The T-cell response to mutated and normal p53 products of BALB/c-derived Meth A sarcoma was analyzed. Meth A p53 is known to have three missense point mutations in codons 132, 168, and 234, and 24 peptides containing wild-type or mutated sequences at the three mutation sites were constructed. Spleen cells from BALB/c or (BALB/c x C57BL/6)F1 mice immunized with p53 peptides were sensitized in vitro with the corresponding peptides. Because Meth A is resistant to cytotoxic T cells, the sensitive P1-HTR cell line, which expresses a low level of p53 lacking the Meth A p53 mutations, was chosen as a target, either pulse-labeled with p53 peptides or transfected with plasmids containing coding sequences from Meth A p53. One peptide, a nonamer containing the codon 234 mutation (234CM), induced CD8+ cytotoxic T cells that lysed 234CM-pulsed P1-HTR cells in an H-2Kd-restricted fashion. P1-HTR cells pulsed with the corresponding wild-type peptide were only weakly lysed by 234CM-reactive cytotoxic T cells. P1-HTR cells pulsed with other wild-type or mutated p53 peptides were not lysed by 234CM-reactive cytotoxic T cells, nor could these peptides, including 234CW (the wild-type counterpart to 234CM), elicit cytotoxic cells. P1-HTR cells transfected with plasmids coding for the 234CM sequence and expressing high p53 levels were weakly lysed by 234CM-reactive cytotoxic T cells. However, lysis of one of the transfectants was significantly increased by pretreatment with interferon gamma. A proliferative response of CD4+ T cells was elicited by immunization with 234CM and 234CW, but not with other p53-related peptides. The specificity of 234CM-induced CD4+ T cells for 234-region peptides was broader than the reactivity of 234CM-reactive cytotoxic T cells. Mice immunized with 234CM in incomplete Freund's adjuvant showed heightened resistance to Meth A challenge.
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PMID:A mouse mutant p53 product recognized by CD4+ and CD8+ T cells. 790 59


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