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)

Glycophosphatidylinositol (GPI)-anchored membrane proteins are initially synthesized with a cleavable COOH-terminal extension that signals anchor attachment. Overexpression in COS cells of hGH-DAF fusion proteins containing the GPI signal of decay accelerating factor (DAF) fused to the COOH-terminus of human growth hormone (hGH), produces both GPI-anchored hGH-DAF and uncleaved precursors that retain the GPI signal. Using hGH-DAF fusion proteins containing a mutated, noncleavable GPI signal, we show that uncleaved polypeptides are retained inside the cell and accumulate in a brefeldin A-sensitive, Golgi-like juxtanuclear structure. Retention requires the presence of either a functional or a noncleavable GPI signal; hGH-DAF fusion proteins containing only the COOH-terminal hydrophobic domain (a component of the GPI signal) are secreted. Immunofluorescence analysis shows colocalization of the retained, uncleaved fusion proteins with both a Golgi marker and with p53, a marker of the ER-Golgi intermediate compartment. Since N-linked glycosylation is postulated to facilitate the transport of proteins to the cell surface, we engineered a glycosylation site into hGH-DAF. Glycosylation failed to completely override the transport block, but allowed some uncleaved hGH-DAF to pass through the secretory pathway and acquire endoglycosidase H resistance. The retained molecules remained endoglycosidase H sensitive. We suggest that the uncleaved fusion protein is retained in a sorting compartment between the ER and the medial Golgi complex. We speculate that a mechanism exists to retain proteins containing an uncleaved GPI signal as part of a system for quality control.
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PMID:Proteins containing an uncleaved signal for glycophosphatidylinositol membrane anchor attachment are retained in a post-ER compartment. 138 43

The wild-type p53 protein functions to suppress transformation, but numerous mutant p53 proteins are transformation competent. To examine the role of p53 as a transcription factor, we made fusion proteins containing human or mouse p53 sequences fused to the DNA binding domain of a known transcription factor, GAL4. Human and mouse wild-type p53/GAL4 specifically transactivated expression of a chloramphenicol acetyltransferase reporter in HeLa, CHO, and NIH 3T3 cells. Several mutant p53 proteins, including a mouse p53 mutant which is temperature sensitive for suppression, were also analyzed. A p53/GAL4 fusion protein with this mutation was also transcriptionally active only at the permissive temperature. Another mutant p53/GAL4 fusion protein analyzed mimics the mutation inherited in Li-Fraumeni patients. This fusion protein was as active as wild-type p53/GAL4 in our assay. Two human p53 mutants that arose from alterations of the p53 gene in colorectal carcinomas were 30- to 40-fold less effective at activating transcription than wild-type p53/GAL4 fusion proteins. Thus, functional wild-type p53/GAL4 fusion proteins activate transcription, while several transformation competent mutants do so poorly or not at all. Only one mutant p53/GAL4 fusion protein remained transcriptionally active.
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PMID:Analysis of p53 mutants for transcriptional activity. 194 76

We have identified a region of human p53 protein with striking homology to a sequence motif on Simian Virus 40 T antigen which includes the nuclear localisation signal. Mutation of basic amino acid residues in this region of p53 (residues 312 to 323; SSSPQPKKKP) compromises transport of p53 protein to the nucleus. The sequence functions efficiently as a nuclear localisation signal when fused to E. coli beta galactosidase. Serine 315 within this p53 structural motif is phosphorylated in vitro by the cell cycle kinase p34cdc2. Thus in both T antigen and p53, nuclear localisation signal and p34cdc2 kinase acceptor residue map to a contiguous region of primary amino acid sequence.
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PMID:The p53 nuclear localisation signal is structurally linked to a p34cdc2 kinase motif. 215 9

Simian virus 40 (SV40)-containing DNA was rescued after the fusion of SV40-transformed VLM cells with permissive COS1 monkey cells and cloned, and prototype plasmid clones were characterized. A 2-kilobase mouse DNA fragment fused with the rescued SV40 DNA, and derived from mouse DNA flanking the single insert of SV40 DNA in VLM cells, was sequenced. Insertion of the intact rescued mouse sequence, or two nonoverlapping fragments of it, into wild-type SV40 plasmid DNA suppressed replication of the plasmid in TC7 monkey cells, although the plasmids expressed replication-competent T antigen. Rat cells were transformed with linearized wild-type SV40 plasmid DNA with or without fragments of the mouse DNA in cis. Although all of the rat cell lines expressed approximately equal amounts of T antigen and p53, transformants carrying SV40 DNA linked to either of the same two replication suppressor fragments produced significantly less free SV40 DNA after fusion with permissive cells than those transformed by SV40 DNA without a cellular insert or with a cellular insert lacking suppressor activity. The results suggest that two independent segments of cellular DNA act in cis to suppress SV40 replication in vivo, either as a plasmid or integrated in chromosomal DNA.
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PMID:cis-active elements from mouse chromosomal DNA suppress simian virus 40 DNA replication. 215 49

Protein import into the cell nucleus requires specific binding of nuclear proteins to the nuclear pore complex. Based on amino acid sequence "motifs" of known nuclear targeting signals, we identified peptides within a number of nuclear proteins with likely nuclear targeting potential and tested their function by transfecting into cells fusion genes that produce the cytoplasmic "reporter" protein, pyruvate kinase (PK), joined to the test sequence. Sequences within c-myb (PLLKKIKQ), N-myc (PPQKKIKS), p53 (PQPKKKP), and c-erb-A (SKRVAKRKL) oncoproteins that direct PK hybrids into the nucleus were identified. A peptide (GRKKRRQRRRAP) of the human immunodeficiency virus (HIV) tat protein (Tat), which contains two short basic regions, targets fusion proteins to the nucleolus. The COOH-terminal basic Tat region (QRRRAP) does not target PK hybrid proteins into the nucleus, but mutation of two basic amino acids in this region decreases but does not abolish nucleolar accumulation mediated by the entire Tat nucleolar targeting sequence. Moreover, the c-Myc nuclear targeting sequence fused to the COOH-terminal basic Tat region (PAAKRVKLDQRRRAP) effectively localizes PK hybrids to the nucleus and nucleolus. A similar sequence (FKRKHKKDISQNKRAVRR) in the human heat-shock protein HSP70 also localizes PK to the nucleus and nucleolus.
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PMID:Nuclear and nucleolar targeting sequences of c-erb-A, c-myb, N-myc, p53, HSP70, and HIV tat proteins. 255 99

The bcr gene plays a critical role in the pathogenesis of two human leukemias associated with the Philadelphia chromosome: chronic myelogenous leukemia (CML) and acute lymphoblastic leukemia (ALL). In both instances a chimeric gene, formed between bcr and the abl protooncogene, results in expression of fused bcr-abl proteins with tyrosine kinase activity. There is controversy regarding the normal gene products of bcr. We investigated this problem by several techniques and found proteins of 190/185, 155, 135, 125, 108, 83 and 47 kDa in several human cell lines by immunoprecipitation with two distinct site-directed anti-bcr antibodies termed anti-bcr(738-753) and anti-bcr(898-911). The 190/185, 155, 125 and 108 kDa proteins were consistently detected by anti-bcr(898-911) antibodies by immunoblotting. Antibodies pre-reacted with excess bcr peptide did not detect these proteins. These proteins were labeled with [32P]orthophosphate in vivo and in vitro by [gamma 32P]ATP in immune complex kinase assays performed with anti-bcr antibodies indicating that these proteins are phosphorproteins. Following labeling in kinase assays, phosphoamino acid analyses detected both phosphoserine and phosphothreonine. In structural studies using one dimensional peptide maps derived by partial V8 protease treatment, the 185, 155, 135, 125 and 108 kDa proteins shared several peptide fragments but contained unique fragments as well. Similarly 2-dimensional maps of proteins labeled in the kinase assay exhaustively digested with trypsin, revealed homology between the 155, 135, 125, 108, and 83 kDa proteins. bcr proteins sedimented in glycerol gradients as putative complexes detected in the cytoplasm of the cell. A 47 kDa protein as well as the recently identified Ph-P53 protein appeared to be associated with bcr proteins based on their co-sedimentation in glycerol gradients and co-immunoprecipitation with several different anti-bcr antibodies. None of the proteins exhibited a precursor-product relationship in pulse-chase experiments conducted with [35S]methionine. We conclude that human cells express several different bcr gene products ranging in size from 190 to 83 kDa, and that these proteins can form specific intracellular cytoplasmic complexes with other cellular proteins.
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PMID:Characterization of bcr gene products in hematopoietic cells. 264 52

Transcriptional deregulation of the p53 gene may play an important part in the genesis of some tumors. We report here an accurate determination of the transcriptional start sites of the human p53 gene and show that the majority of p53 mRNA molecules do not contain a postulated stem-loop structure at their 5' ends. Recombinant plasmids of the human p53 promoter-leader region fused to the bacterial chloramphenicol acetyltransferase gene (cat) were constructed. After transfection into rodent or human cells, a 350-base-pair fragment spanning the promoter region conferred 4% of the CAT activity mediated by the simian virus 40 early promoter/enhancer. We monitored the efficiency with which 15 3' and 5' promoter deletion constructs initiated transcription. Our results show that an 85-base-pair fragment, previously thought to have resided in exon 1, is all that is required for full promoter activity.
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PMID:Characterization of the human p53 gene promoter. 266 71

Leukemic cells from patients with Philadelphia chromosome (Ph1)-positive chronic myelogenous leukemia (CML) contain a 210 kDa protein (P210bcr-abl) with a protein tyrosine kinase activity that is a product of fused bcr and abl genes. We have prepared two monoclonal anti-peptide antibodies, one from each gene product, and have affinity purified each. Incubation of anti-abl (c-abl 51-64) immunoprecipitates of K562 cells with [gamma-32P]ATP in protein kinase assays resulted in the labeling of P210bcr-abl and a 53 kDa (ph-P53) protein. Increasing concentrations of antibody detected similar ratios of P210bcr-abl: ph-P53, suggesting the presence of a complex between the proteins. Several different anti-abl and anti-bcr antibodies detected the ph-P53/P210 complex. Sodium dodecyl sulfate (SDS) treatment without 2-mercaptoethanol eluted P210bcr-abl and ph-P53 from the monoclonal antibody in the form of complexes which migrated on 6% SDS-polyacrylamide gels and had apparent molecular weights of 275,000 and more than 500,000. Both complexes yielded ph-P53 and P210bcr-abl upon treatment with SDS-mercaptoethanol. Studies involving glycerol gradient centrifugation also detected complexes of P210bcr-abl and ph-P53. Our results indicate that ph-P53 is not a degraded product of P210bcr-abl, does not share antigenic determinants with P210bcr-abl since it is not recognized by anti-abl and bcr antibodies in immunoblots, is not the phosphorylated heavy chain of immunoglobulin G, and is different from p53 (the nonviral T protein) complexed to the large T antigen of simian virus 40. Previous studies (Maxwell et al., 1987) have shown that ph-P53 has a different peptide map than P210bcr-abl. Therefore, we conclude that ph-P53 is a distinct cellular protein complexed to P210bcr-abl in K562 cells.
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PMID:A novel 53 kDa protein complexed with P210bcr-abl in human chronic myelogenous leukemia cells. 313 27

Analysis of Abelson murine leukemia virus-transformed L12 cells which lack the p53 cellular encoded tumor antigen revealed alterations in the p53-specific genomic DNA sequences. The active p53 gene, usually contained in a 16-kilobase EcoRI DNA fragment of p53 producer cells, went through major alterations leading to the appearance of a substantially larger 28.0-kilobase p53-specific EcoRI fragment. Detailed restriction enzyme analysis, with genomic probes spanning throughout the whole active p53 gene, indicated that the L12 p53 altered gene contains all the exons and principal introns of the normal p53 16.0-kilobase gene. However, its structure was interrupted by the integration of a novel DNA segment into the noncoding intervening sequences of the first p53 intron. Analysis of the inserted sequences revealed close homology to Moloney murine leukemia virus. This Moloney leukemia murine virus-like particle resides in a 5' to 3' transcriptional orientation, similar to the p53 gene, permitting the transcription of aberrant fused mRNA molecules detected in these cells.
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PMID:Inactivation of p53 gene expression by an insertion of Moloney murine leukemia virus-like DNA sequences. 609 69

Rb represses E2F-mediated transcription in part by blocking the trans-activation domain of E2F. In addition, Rb can convert an E2F binding site from a positive to a negative element. To examine the effect of a Rb-DNA-bound complex on transcription, full-length Rb was fused to the DNA binding domain of GAL4. Here, we report that GAL4-Rb can repress transcription mediated by either Sp1, AP-1, or p53, dependent upon the presence of both the GAL4 DNA binding domain and GAL4 binding sites. Moreover, GAL4-Rb inhibited the activity of the herpes simplex virus tk promoter from GAL4 binding sites located at a distance from the promoter. In contrast, GAL4-Rb was unable to repress basal transcription. Cotransfection of specific cyclins and cyclin-dependent kinases or SV40 T-antigen abolished the repressive activity of GAL4-Rb. The domains of Rb involved in mediating the repression of transcription were mapped to regions that are overlapping, but not identical, to those required for the interaction with E2F. We propose that Rb can function as a general repressor of transcription when bound to the promoter region.
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PMID:The retinoblastoma susceptibility gene product represses transcription when directly bound to the promoter. 772 91


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