Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UNIPROT:P04637 (p53)
 77,613 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Transfection of the wild-type p53 gene into malignant cell lines usually results in an inhibition of proliferation. However, the physiological function of the endogenous p53 gene product has been difficult to ascertain. In order to examine whether p53 is involved in the regulation of proliferation and/or differentiation of hematopoietic tissue, we modified a recently developed flow cytometric assay to assess p53 protein expression in normal human hematopoietic cells, primary leukemias, and selected leukemia cell lines. In normal human bone marrow, p53 protein was not detected in the proliferative, progenitor cell populations identified by the cell surface antigens CD34 (progenitor cells of multiple lineages) or glycophorin (erythroid precursors). In contrast, low but detectable levels of p53 protein were observed in the nonproliferative, mature lymphoid, granulocytic, and monocytic cell populations. Similarly, p53 levels increased and DNA synthesis decreased during 12-O-tetradecanoylphorbol-13-acetate-induced differentiation of ML-1 myeloblastic leukemia cells. Both of these results suggest that endogenous, wild-type p53 protein may play a role in hematopoietic cell maturation, possibly by contributing to the inhibition of proliferation that occurs during terminal differentiation. Leukemia cells deviated from this pattern of expression: (a) in contrast to the normal, proliferative bone marrow progenitor cells, a significant percentage of patient leukemia samples expressed detectable levels of p53 protein; and (b) leukemia cell lines exhibited lineage-specific abnormalities in p53 expression, with overexpression in lymphoid cell lines and lack of expression in myeloid cell lines.
 ...
PMID:Levels of p53 protein increase with maturation in human hematopoietic cells. 186 48

The inhibition of replicative DNA synthesis that follows DNA damage may be critical for avoiding genetic lesions that could contribute to cellular transformation. Exposure of ML-1 myeloblastic leukemia cells to nonlethal doses of the DNA damaging agents, gamma-irradiation or actinomycin D, causes a transient inhibition of replicative DNA synthesis via both G1 and G2 arrests. Levels of p53 protein in ML-1 cells and in proliferating normal bone marrow myeloid progenitor cells increase and decrease in temporal association with the G1 arrest. In contrast, the S-phase arrest of ML-1 cells caused by exposure to the anti-metabolite, cytosine arabinoside, which does not directly damage DNA, is not associated with a significant change in p53 protein levels. Caffeine treatment blocks both the G1 arrest and the induction of p53 protein after gamma-irradiation, thus suggesting that blocking the induction of p53 protein may contribute to the previously observed effects of caffeine on cell cycle changes after DNA damage. Unlike ML-1 cells and normal bone marrow myeloid progenitor cells, hematopoietic cells that either lack p53 gene expression or overexpress a mutant form of the p53 gene do not exhibit a G1 arrest after gamma-irradiation; however, the G2 arrest is unaffected by the status of the p53 gene. These results suggest a role for the wild-type p53 protein in the inhibition of DNA synthesis that follows DNA damage and thus suggest a new mechanism for how the loss of wild-type p53 might contribute to tumorigenesis.
 ...
PMID:Participation of p53 protein in the cellular response to DNA damage. 2737 38

GADD45 (growth arrest and DNA damage) is a DNA-damage-inducible gene regulated in part by the tumor suppressor p53. A role in negative growth control has recently been suggested based on significant (more than 75%) reduction of colony formation following over expression of Gadd45. To better understand the role of Gadd45, we have developed specific rabbit and murine antibodies raised against the human recombinant protein. Using these antibodies, we have found that in ML-1 cells Gadd45 is predominantly a nuclear protein. MyD118, a protein induced by terminal differentiation sharing 57% homology with Gadd45, does not cross-react with any of the antibodies produced. As expected, the induction of Gadd45 protein by ionizing radiation (IR) was also found to be dependent on a wild type p53 phenotype. Interestingly, WI-L2-NS, a human lymphoid cell line, showed very high basal levels of Gadd45 mRNA and protein in addition to a high constitutive level of a mutated p53 protein. In this cell line, the high levels of GADD45 did not inhibit cellular growth in spite of the fact that no mutations were found in GADD45 sequence. These results indicate that some cell line(s) can tolerate high levels of Gadd45 and abrogate its growth suppression function.
 ...
PMID:Characterization of human Gadd45, a p53-regulated protein. 779 74

DNA-damaging agents such as ionizing radiation (IR) activate the tumor suppressor p53 and in some cases can cause apoptosis. M1 cells, which do not express the endogenous tumor suppressor gene p53, undergo apoptosis following activation of a temperature sensitive p53 transgene, where it has been shown that bax, an important mediator of apoptosis, is a p53 target gene (Selvakumaran et al, Oncogene 9, 1791-8, 1994). Since p53 can function as a transcription factor after activation by IR, the genetic response to this stress was examined in a panel of human cells with defined p53 status. Like the p53-regulated gene gadd45, bax was rapidly induced, as measured by increased mRNA levels, in the p53 wt (wild type) human myeloid line ML-1, and it was not induced in cells lacking functional p53. However, unlike other p53-regulated genes, bax was only induced in p53 wt cells in which IR also triggered apoptosis. In the case of bcl2, which opposes bax function, mRNA levels were reduced in ML-1 cells after IR. Thus, bax appears to be an unique p53-regulated gene in that its induction by IR not only requires functional p53 but also requires that the cells be apoptosis "proficient."
 ...
PMID:Induction of bax by genotoxic stress in human cells correlates with normal p53 status and apoptosis. 797 Jul 35

The production of two different murine monoclonal antibodies to human Gadd45, a protein that is induced in response to DNA damage, is reported. Antibodies were generated in a SJL mouse using a recombinant form of the human Gadd45 protein. Monoclonal antibody 4TCYA1, which recognizes the denatured form of human Gadd45 in Western blots, was selected based upon the recognition of Gadd45 induced by functional p53 in the human myeloid leukemia cell line, ML-1. A second monoclonal antibody, designated 30T.14, immunoprecipitates native human Gadd45 in lysates produced from RKO cells, a colorectal carcinoma cell line that expresses relatively high basal levels of Gadd45, as well as from cell lysates made from ML-1 cells after exposure to ionizing irradiation (IR). Since 4TCYA1 fails to immunoprecipitate Gadd45, and 30T.14 fails to bind to IR-induced Gadd45 in immunoblotting, these two monoclonal antibodies probably recognize different epitopes.
 ...
PMID:The production and characterization of murine monoclonal antibodies to human Gadd45 raised against a recombinant protein. 852 47

Deferoxamine (DFO)-induced iron deprivation caused an increase in p53 expression in ML-1 and Raji cells. In ML-1 cells, with express wild type p53, p53 protein levels were transiently increased 6 h after addition of 10(-4)M DFO. In Raji cells, which carry a mutant p53 allele, p53 increased 6 h after addition of 10(-4)M DFO and remained elevated for 24 h. Growth inhibition was observed in both cell types 6 h after addition of 10(-4)M DFO. In both cells, p53 mRNA levels did not increase following incubation with DFO, suggesting that increased p53 expression is the result of a post-transcriptional mechanism. Although increases in wild type p53 protein in ML-1 cells resulted in increases in a p53 target gene, p21cipl/wafl/sdil, this effect was not observed in Raji cells which express a mutant p53 protein.
 ...
PMID:Iron deprivation results in an increase in p53 expression. 859 Jun 32

When ML-1 human myeloid leukemia cells are exposed to DNA damaging agents, they exhibit dramatic changes in the expression of a variety of gene products. This includes an increase in p53 (wild-type), a decrease in BCL2, a p53-dependent increase in the BCL2 family member BAX, and increases in Growth Arrest and DNA Damage-inducible (GADD) genes such as GADD45; these changes occur as early events in a sequence that culminates in DNA damage-induced apoptosis. DNA damaging agents have now been tested for effects on expression of another BCL2 family member, MCL1, a gene expressed during ML-1 cell differentiation. Expression of MCL1 was found to increase upon exposure of ML-1 cells to various types of DNA damaging agents, including ionizing radiation, ultraviolet radiation, and alkylating drugs. The increase in MCL1 occurred rapidly and was transient, levels of the MCL1 mRNA being elevated within 4 h and having returned to near baseline within 24 h. An increase in the Mcl1 protein was also seen, with the maximal increase occurring at an intermediate dose of IR (5 Gray) and lesser increases occurring at either lower or higher doses. The increase in expression of MCL1 was further studied using a panel of human cell lines that includes cells containing or not containing alterations in p53 as well as cells sensitive or insensitive to the apoptosis-inducing effects of DNA damage. The DNA damage-induced increase in MCL1 mRNA did not depend upon p53 as it was seen in cells lacking functional p53. However, the increase did depend upon susceptibility to apoptosis as it was not seen in cells insensitive to apoptosis-induction by DNA damaging agents. These findings demonstrate that cytotoxic DNA damage causes an increase in the expression of MCL1 along with increases in GADD45 and BAX and a decrease in BCL2. Furthermore, while the increase in GADD45 is seen both in cells that undergo growth arrest and in cells that undergo apoptosis in response to DNA damage, alterations in the profile of expression of BCL2 family members occur exclusively in cells that undergo the apoptotic response, with some family members increasing through p53-dependent (BAX) and others through p53-independent (MCL1) pathways. Overall, expression MCL1 can increase during the induction of cell death as well as during the induction of differentiation.
 ...
PMID:Induction of BCL2 family member MCL1 as an early response to DNA damage. 907 Jun 51

The tumor suppressor protein p53 has a transcriptional activation activity thought to mediate its biologic function including G1 arrest and perhaps apoptosis. To learn more about p53's transactivator function in vivo, we performed genomic footprinting experiments examining p53-DNA interactions in the regulatory regions of the p53-regulated genes p21, GADD45, and MDM2. Using ionizing radiation to induce DNA damage in human ML-1 myeloblastic leukemia cells, the promoter and intronic regions of these genes containing p53-consensus binding sites were examined for in vivo footprints. There was a uniform and sustained expression of p53 protein as well as a strong induction of p21, GADD45, and MDM2 mRNA following irradiation. At the two p53 consensus binding sites in the p21 promoter, reduced DNaseI cleavage was observed in irradiated cells beginning 1 to 2h after irradiation, being most pronounced after 2 h and diminishing after 8 h. A partial in vivo footprint was also observed in the third intron of the GADD45 gene beginning 2 h after irradiation. No in vivo footprints were seen at the two p53 binding sites in the MDM2 gene. Our study provides direct evidence that the DNA damage-induced activity of p53 is mediated by its consensus DNA binding sites in the p21 and GADD45 genes. We suggest that the transient nature and relative instability of p53-DNA interactions in vivo may make the p53 protein more accessible to a rapid turnover pathway which might be impaired under conditions when the protein is stably bound to DNA.
 ...
PMID:In vivo evidence for binding of p53 to consensus binding sites in the p21 and GADD45 genes in response to ionizing radiation. 923 81

p53 is able to recognize and bind sites of DNA damage and, in some way, damage to cellular DNA activates a p53 response leading to G1 arrest or apoptosis. We have previously shown that 'damaged DNA' induces N-terminal cleavage of p53 to generate p40(DeltaN) and p35 (core) protein products. We now show that the p35 product has protease activity and is able to cleave between residues 23 and 24 of full-length p53 to generate a novel product, p50(DeltaN23). This activity was inhibited by bestatin, an aminopeptidase inhibitor. Residues 23 and 24 lie within the mdm-2 binding domain of p53 and the possibility that p50(DeltaN23) may be resistant to feedback regulation by mdm-2 is discussed. Unexpectedly, interaction with ssDNA induced two further cleavage products of p53, generated by C-terminal cleavage and designated p50(DeltaC) and p40(DeltaC). In vivo generation of a C-terminal cleavage product of endogenous p53 similar in size to p50(DeltaC) correlated with up-regulation of p21 expression in ML-1 cells exposed to either adriamycin or cisplatin. The possible significance of the various p53 cleavage products in relation to the cellular response to DNA damage is discussed.
 ...
PMID:Induced N- and C-terminal cleavage of p53: a core fragment of p53, generated by interaction with damaged DNA, promotes cleavage of the N-terminus of full-length p53, whereas ssDNA induces C-terminal cleavage of p53. 931 58

Data are presented demonstrating that DNA damage leads to specific post-translational modifications of p53 protein. Using two-dimensional peptide mapping of in vivo radiolabeled p53 tryptic phosphopeptides, recombinant truncated p53 protein, and synthetic p53 tryptic peptides, a unique p53 phosphopeptide was identified after exposure of ML-1 cells to ionizing irradiation. This peptide represents the first 24 amino acids of p53 and contains three phosphorylated serine residues. A specific p53 phosphopeptide antibody identified serine-15 as one of the two serines in p53 that becomes phosphorylated following DNA damage induced by either ionizing irradiation (IR) or ultraviolet (UV) irradiation in multiple cell types. IR-induced phosphorylation of p53 does not affect the kinetics of p53 binding to or dissociating from DNA as assessed by electrophoretic mobility-shift assays. However, p53 phosphorylation induced by DNA damage correlates with enhanced transcription of downstream p53 target genes. Low levels of phosphoserine-15 p53 are detectable within 6 hr after IR in AT cells, whereas lymphoblasts from normal individuals exhibit this modification within 1 hr. In contrast, phosphorylation of p53 on serine-15 is similar in normal and AT cells after UV irradiation. Our results indicate that p53 is phosphorylated in response to DNA damage, that this de novo phosphorylation may be involved in the subsequent induction and activation of p53, and that although ATM affects the kinetics of p53 phosphorylation after IR, it is not absolutely required for phosphorylation of p53 on serine-15.
 ...
PMID:DNA damage induces phosphorylation of the amino terminus of p53. 940 38


1 2 3 4 Next >>