Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Repetitive DNA elements frequently are precursors to chromosomal deletions in prokaryotes and lower eukaryotes. However, little is known about the relationship between repeated sequences and deletion formation in mammalian cells. We have created a novel integrated plasmid-based recombination assay to investigate repeated sequence instability in human cells. In a control cell line, the presence of direct or inverted repeats did not appreciably influence the very low deletion frequencies (2 x 10(-7) to 9 x 10(-7)) in the region containing the repeat. Similar to what has been observed in lower eukaryotes, the majority of deletions resulted from the loss of the largest direct repeat present in the system along with the intervening sequence. Interestingly, in closely related cell lines that possess a mutant p53 gene, deletion frequencies in the control and direct-repeat plasmids were 40 to 300 times higher than in their wild-type counterparts. However, mutant p53 cells did not preferentially utilize the largest available homology in the formation of the deletion. Surprisingly, inverted repeats were approximately 10,000 times more unstable in all mutant p53 cells than in wild-type cells. Finally, several deletion junctions were marked by the addition of novel bases that were homologous to one of the preexisting DNA ends. Contrary to our expectations, only 6% of deletions in all cell lines could be classified as arising from nonhomologous recombination.
Mol Cell Biol 2000 Jun
PMID:Homologous and nonhomologous recombination resulting in deletion: effects of p53 status, microhomology, and repetitive DNA length and orientation. 1080 45

Anticancer nucleoside analogs (e.g., ara-C, gemcitabine, fludarabine) induce apoptosis by incorporation into DNA. Removal of incorporated analogs from DNA by 3'-5' exonucleases is presumably a mechanism of drug resistance. Based on our previous observation that the 3'-5' exonuclease activity of wild-type (wt) p53 protein is able to preferentially remove mismatched nucleotides from DNA, in the present study we further investigated the ability of p53 to recognize and remove incorporated therapeutic analogs from DNA and its role in analog-induced apoptosis. We demonstrated that although the 3'-5' exonuclease of wt p53 protein was able to bind and excise the nucleoside analog residues from DNA in vitro, removal of the drug molecules from cellular DNA was slow in whole cells with wt p53 cells, and not detectable in mutant p53 cells. Furthermore, the wt p53 were more sensitive to the cytotoxic effect of the drugs compared to the p53-null or mutant cells. Incubation of ML-1 cells (wt p53) with gemcitabine caused an accumulation of p53 protein in their nuclei and preferentially induced apoptosis in the p53-positive cells, whereas the p53-negative cells remained intact. Transfection of p53-null cells with wt p53 expression vector enhanced the sensitivity of the cells to gemcitabine. Gel mobility shift assay using synthetic DNA containing gemcitabine as the probe suggests that p53 protein is likely to participate in the binding of the analog-containing DNA. Our study suggests that recognition of the incorporated nucleoside analogs in DNA by wt p53 did not confer resistance to the drugs, but it facilitated the apoptotic cell death process.
Int J Mol Med 2000 Jun
PMID:Role of p53 in cellular response to anticancer nucleoside analog-induced DNA damage. 1081 7

An important issue for effective vaccines is the development of potent adjuvants that can facilitate induction or augmentation of immunity. Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a growth factor for myeloid progenitors of monocytes and dendritic cells (DC), which upon maturation are antigen-presenting cells (APC). The adjuvant effects of inoculation of DNA encoding GM-CSF into skin were studied. Initial experiments examined whether the GM-CSF gene injected into the skin of mice could affect the density of epidermal DC (Langerhans cells). DNA encoding GM-CSF delivered by particle bombardment into skin resulted in a significant increase of epidermal DC at the inoculation site. Kinetic analysis of epidermal recruitment after GM-CSF inoculation showed an increase in DC that peaked at seven days. This increase was accompanied by recruitment of DC into draining lymph nodes. The adjuvant effects of DNA encoding GM-CSF inoculated into skin were measured by the ability to augment antibody and T-cell responses against poorly immunogenic tumor antigens. Peptide immunization at skin sites containing epidermal DC newly recruited by GM-CSF DNA elicited T-cell responses against mutant p53, whereas peptide immunization of control skin sites did not elicit any detectable T-cell responses. Likewise, generation of antibodies following immunization with DNA encoding human gp75TRP1, a tyrosinase family member expressed by melanomas, was accelerated and protection from tumor challenge augmented by GM-CSF DNA.
Cytokines Cell Mol Ther 1999 Dec
PMID:Injection of DNA encoding granulocyte-macrophage colony-stimulating factor recruits dendritic cells for immune adjuvant effects. 1085 Mar 86

p53, a tumor suppressor, inhibits cell proliferation by inducing cellular genes involved in the regulation of the cell cycle. MCG10, a novel cellular p53 target gene, was identified in a cDNA subtraction assay with mRNA isolated from a p53-producing cell line. MCG10 can be induced by wild-type but not mutant p53 and by DNA damage via two potential p53-responsive elements in the promoter of the MCG10 gene. The MCG10 gene contains 10 exons and is located at chromosome 3p21, a region highly susceptible to aberrant chromosomal rearrangements and deletions in human neoplasia. The MCG10 gene locus encodes at least two alternatively spliced transcripts, MCG10 and MCG10as. The MCG10 and MCG10as proteins contain two domains homologous to the heterogeneous nuclear ribonucleoprotein K homology (KH) domain. By generating cell lines that inducibly express either wild-type or mutated forms of MCG10 and MCG10as, we found that MCG10 and MCG10as can suppress cell proliferation by inducing apoptosis and cell cycle arrest in G(2)-M. In addition, we found that MCG10 and MCG10as, through their KH domains, can bind poly(C) and that their RNA-binding activity is necessary for inducing apoptosis and cell cycle arrest. Furthermore, we found that the level of the poly(C) binding MCG10 protein is increased in cells treated with the DNA-damaging agent camptothecin in a p53-dependent manner. These results suggest that the MCG10 RNA-binding protein is a potential mediator of p53 tumor suppression.
Mol Cell Biol 2000 Aug
PMID:MCG10, a novel p53 target gene that encodes a KH domain RNA-binding protein, is capable of inducing apoptosis and cell cycle arrest in G(2)-M. 1089 98

The p53 tumor suppressor protein functions as a transcription factor. It has, however, been previously reported that some p53 mutants are able to suppress cell growth independent of their transcriptional activity [Kaneuchi et al., (1999)]. In order to investigate the correlations between the trans-activation and growth-suppressive functions of p53, we have analyzed five p53 mutants by CAT reporter assay, colony formation assay, and growth-rate analysis. Five p53 mutants [Oh et al., (2000)]--199stop (Gly-->stop), 240ile (Ser-->Ile), 250ala (Pro-->Ala), 285lys (Glu-->Lys), and 291asn (Lys-->Asn)--were cotransfected with a reporter construct containing a p53-responsive element and then tested for their trans-activational activity in p53-null Saos-2 cells. As a result of a change in the protein structure, trans-activational activity was negated in 199stop, 240ile, 285lys, and 291asn, while 250ala retained its activity. Colony formation assay revealed that mutants 240ile and 250ala retained their growth suppression, while 199stop, 285lys, and 291asn did not. To study the features of these proteins, a group of isogenic cell lines that express mutant forms of p53 was generated from HeLa cells, and their growth rate was then examined: one group, containing 199stop, 285lys, and 291asn, showed a rapid growth rate, similar to that of the original HeLa cells; the other group, containing 240ile and 250ala, however, exhibited a slow growth rate. In conclusion, mutant p53 240ile, which completely lost its trans-activational activity, nevertheless continued to exhibit its growth-suppressive activity. Further work is required to understand how 240ile is involved in growth suppression.
Mol Cells 2000 Aug 31
PMID:The p53 mutation which abrogates trans-activation while maintaining its growth-suppression activity. 1098 34

The insulin-like growth factor-I receptor (IGF-I-R) has a central role in normal cellular proliferation as well as in transformation processes. Transcription of the IGF-I receptor gene is controlled by a number of tumor suppressors, including WT1, p53, and BRCA1. It has been demonstrated that, in their wild-type form, these transcription factors can suppress the activity of the IGF-I-R promoter, with ensuing reduction in the levels of cell-surface IGF binding. On the other hand, a number of oncogenes, including mutant p53 and c-myb, and the fusion protein EWS-WT1 significantly stimulate promoter activity. Interactions between stimulatory and inhibitory transcription factors may determine the level of expression of the IGF-I-R gene and, consequently, the proliferative status of the cell.
Mol Genet Metab
PMID:Regulation of the insulin-like growth factor-I receptor gene by oncogenes and antioncogenes: implications in human cancer. 1100 24

We have demonstrated previously that the toxicity of 5-hydroxymethyl-2'-deoxyuridine (hmdUrd) to Chinese hamster fibroblasts (V79 cells) results from enzymatic removal of large numbers of hydroxymethyluracil residues from the DNA backbone [Boorstein,R. et al. (1992) Mol. Cell. Biol., 12, 5536-5540]. Here we report that a significant portion of the hmdUrd-induced cell death that is dependent on DNA base excision repair in V79 cells is apoptosis. Incubation of V79 cells with pharmacologically relevant concentrations of hmdUrd resulted in the characteristic changes of apoptosis as measured by gel electrophoresis, flow cytometry and phase contrast microscopy. However, hmdUrd did not induce apoptosis in V79mut1 cells, which are deficient in DNA base excision repair of 5-hydroxymethyluracil (hmUra). Apoptosis was not prevented by addition of 3-aminobenzamide, which inhibits synthesis of poly(ADP-ribose) from NAD, indicating that apoptosis was not the direct consequence of NAD depletion. Pulsed field gel electrophoresis indicated that hmdUrd treatment resulted in high molecular weight (2.2-4.5 Mb) DNA double-strand breaks prior to formation of internucleosomal ladders in V79 cells. Simultaneous measurement of DNA strand breaks with bromodeoxyuridine/terminal deoxynucleotidyl transferase-fluorescein isothiocyanate labeling and of cell cycle distribution indicated that cells with DNA strand breaks accumulated in late S/G(2) and that hmdUrd-treated cells underwent apoptosis after arrest in late S/G(2) phase. Our results indicate that excessive DNA base excision repair results in the generation of high molecular weight DNA double-strand breaks and eventually leads to apoptosis in V79 cells. Thus, delayed apoptosis following DNA damage can be a consequence of excessive DNA repair activity. Immunochemical analysis showed that both V79 and V79mut1 cells contained mutant p53, indicating that apoptosis induced by DNA base excision repair can be independent of p53.
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PMID:Excessive base excision repair of 5-hydroxymethyluracil from DNA induces apoptosis in Chinese hamster V79 cells containing mutant p53. 1115 57

The p53 protein is related by sequence homology and function to the products of two other genes, p63 and p73, that each encode several isoforms. We and others have discovered previously that certain tumor-derived mutants of p53 can associate and inhibit transcriptional activation by the alpha and beta isoforms of p73. In this study we have extended these observations to show that in transfected cells a number of mutant p53 proteins could bind and down-regulate several isoforms not only of p73 (p73 alpha, -beta, -gamma, and -delta) but also of p63 (p63 alpha and -gamma; Delta Np63 alpha and -gamma). Moreover, a correlation existed between the efficiency of p53 binding and the inhibition of p63 or p73 function. We also found that wild-type p63 and p73 interact efficiently with each other when coexpressed in mammalian cells. The interaction between p53 mutants and p63 or p73 was confirmed in a physiological setting by examining tumor cell lines that endogenously express these proteins. We also demonstrated that purified p53 and p73 proteins interact directly and that the p53 core domain, but not the tetramerization domain, mediates this interaction. Using a monoclonal antibody (PAb240) that recognizes an epitope within the core domain of a subset of p53 mutants, we found a correlation between the ability of p53 proteins to be immunoprecipitated by this antibody and their ability to interact with p73 or p63 in vitro and in transfected cells. Based on these results and those of others, we propose that interactions between the members of the p53 family are likely to be widespread and may account in some cases for the ability of tumor-derived p53 mutants to promote tumorigenesis.
Mol Cell Biol 2001 Mar
PMID:A subset of tumor-derived mutant forms of p53 down-regulate p63 and p73 through a direct interaction with the p53 core domain. 1123 24

P53 is a homotetrameric tumor suppressor protein involved in transcriptional control of genes that regulate cell proliferation and death. In order to probe the role that oligomerization plays in this capacity, we have previously designed and characterized a series of p53 proteins with altered oligomeric states through hydrophilc substitution of residues Met340 or Leu344 in the normally tetrameric oligomerization domain. Although such mutations have little effect on the overall secondary structural content of the oligomerization domain, both solubility and the resistance to thermal denaturation are substantially reduced relative to that of the wild-type domain. Here, we report the design and characterization of a double-mutant p53 with alterations of residues at positions Met340 and Leu344. The double-mutations Met340Glu/Leu344Lys and Met340Gln/Leu344Arg resulted in distinct dimeric forms of the protein. Furthermore, we have verified by NMR structure determination that the double-mutant Met340Gln/Leu344Arg is essentially a "half-tetramer". Analysis of the in vivo activities of full-length p53 oligomeric mutants reveals that while cell-cycle arrest requires tetrameric p53, transcriptional transactivation activity of monomers and dimers retain roughly background and half of the wild-type activity, respectively.
J Mol Biol 2001 Mar 23
PMID:Structure and functionality of a designed p53 dimer. 1125 85

Transcriptional silencing of tumor suppressor genes by DNA methylation occurs in cancer cell lines and in human tumors. This has led to the pursuit of DNA methyltransferase inhibition as a drug target. 5-Aza-2'-deoxycytidine [5-aza-CdR (decitabine)], a potent inhibitor of DNA methyltransferase, is a drug currently in clinical trials for the treatment of solid tumors and leukemia. The efficacy of 5-aza-CdR may be related to the induction of methylation-silenced tumor suppressor genes, genomic hypomethylation, and/or enzyme-DNA adduct formation. Here, we test the hypothesis that 5-aza-CdR treatment is perceived as DNA damage, as assessed by the activation of the tumor suppressor p53. We show that 1) colon tumor cell lines expressing wild-type p53 are more sensitive to 5-aza-CdR mediated growth arrest and cytotoxicity; 2) the response to 5-aza-CdR treatment includes the induction and activation of wild-type but not mutant p53 protein; and 3) the induction of the downstream p53 target gene p21 is partially p53-dependent. The induction of p53 protein after 5-aza-CdR treatment did not correlate with an increase in p53 transcripts, indicating that hypomethylation at the p53 promoter does not account for the p53 response. It is relevant that 5-aza-CdR has shown the greatest promise in clinical trials for the treatment of chronic myelogenous leukemia, a malignancy in which functional p53 is often retained. Our data raise the hypothesis that p53 activation may contribute to the clinical efficacy and/or toxicity of 5-aza-CdR.
Mol Pharmacol 2001 Apr
PMID:Activation of the p53 DNA damage response pathway after inhibition of DNA methyltransferase by 5-aza-2'-deoxycytidine. 1125 19


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