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

Activation of the spi-1/PU.1 proto-oncogene and loss of p53 function are genetic alterations associated with the emergence of Friend malignant erythroleukemic cells. To address the role of p53 during erythroleukemogenesis, spi-1 transgenic mice (spi-1-Tg) which develop erythroleukemia were bred with p53-deficient mice. Three classes of spi-1 transgenic mice differing in their p53 functional status (p53(+/+), p53(+/-) and p53(-/-)) were generated. These mice developed a unique pattern of erythroleukemia. In wild-type p53 spi-1-Tg mice, none of the primary erythroleukemic spleen cells displayed autonomous growth in vitro and in vivo. In contrast, in p53(+/-) spi-1-Tg mice, erythroleukemic cells gave rise to growth factor-independent cell lines and generated tumors in vivo. Malignancy was associated with loss of the wild-type p53 allele. The p53(-/-) spi-1-Tg mice developed erythroleukemia with a total incidence and a reduced latency compared to the two other genotypes. Unexpectedly, 50% of p53(-/-) spi-1-Tg erythroleukemic spleens generated cell lines that were strictly dependent upon erythropoietin (Epo) for proliferation, whereas the remainder proliferated independently of cytokines. Moreover, only 70% of these spleen cells were tumorigenic. These findings indicate that p53 germ-line deletion did not confer malignancy to spi-1-transgenic proerythroblasts. Moreover Epo independence and tumorigenicity appear as separable phenotypic characteristics revealing that the spi-1-Tg proerythroblasts progress towards malignancy through multiple oncogenic events.
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PMID:Germ-line deletion of p53 reveals a multistage tumor progression in spi-1/PU.1 transgenic proerythroblasts. 1157 46

Cancer is a multi-step, multi-genetic event. Whether oncogenic mutations cooperate with one another to transform cells and how is not well understood. The Friend murine retroviral erythroleukemia model involves mitogenic activation of the erythropoietin receptor (EpoR) by the virus env gene (F-gp55), aberrant over-expression of the transcription factor PU.1, and inactivating mutations in p53. In this report we demonstrate that concurrent expression of F-gp55 and PU.1 in erythroid target cells, in vivo, cooperate to accelerate erythroleukemia induction. Early in the disease, prior to the detection of clonal leukemic cells, activation of the EpoR by F-gp55, but not erythropoietin, resulted in transcriptional upregulation of PU.1 through a trans regulatory mechanism. This could occur in the absence of an integrated provirus within the PU.1 gene locus. The regulation of PU.1 transcription in established erythroleukemia cell lines differed depending upon the level of PU.1 protein present. Our results suggest that the action of F-gp55 contributes to both early and late stages of Friend erythroleukemia and that persistence of F-gp55 expression may be required not only to initiate erythroleukemia but to also maintain erythroleukemia following Friend virus infection.
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PMID:Oncogene cooperativity in Friend erythroleukemia: erythropoietin receptor activation by the env gene of SFFV leads to transcriptional upregulation of PU.1, independent of SFFV proviral insertion. 1185 Aug 47

Granulocytes and monocytes develop from a common myeloid progenitor. Early granulopoiesis requires the C/EBPalpha, PU.1, RAR, CBF, and c-Myb transcription factors, and terminal neutrophil differentiation is dependent upon C/EBPepsilon, PU.1, Sp1, CDP, and HoxA10. Monopoiesis can be induced by Maf-B, c-Jun, or Egr-1 and is dependent upon PU.1, Sp1, and ICSBP. Signals eminating from cytokine receptors modulate factor activities but do not determine cell fates. Orchestration of the myeloid developmental program is achieved via cooperative gene regulation, via synergistic and inhibitory protein-protein interactions, via promoter auto-regulation and cross-regulation, via regulation of factor levels, and via induction of cell cycle arrest: For example, c-Myb and C/EBPalpha cooperate to activate the mim-1 and NE promoters, PU.1, C/EBPalpha, and CBF, regulate the NE, MPO, and M-CSF Receptor genes. PU.1:GATA-1 interaction and C/EBP suppression of FOG transcription inhibits erythroid and megakaryocyte gene expression. c-Jun:PU.1, ICSBP:PU.1, and perhaps Maf:Jun complexes induce monocytic genes. PU.1 and C/EBPalpha activate their own promoters, C/EBPalpha rapidly induces PU.1 and C/EBPepsilon RNA expression, and RARalpha activates the C/EBPepsilon promoter. Higher levels of PU.1 are required for monopoiesis than for B-lymphopoiesis, and higher C/EBP levels may favor granulopoiesis over monopoiesis. CBF and c-Myb stimulate proliferation whereas C/EBPalpha induces a G1/S arrest; cell cycle arrest is required for terminal myelopoiesis, perhaps due to expression of p53 or hypo-phosphorylated Rb.
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PMID:Transcriptional regulation of granulocyte and monocyte development. 1203 76

Retroviruses lacking oncogenes have been known to induce various types of cancer when inoculated into animals. Among these, Friend virus, discovered by Charlotte Friend in 1957, is capable of inducing erythroleukemias when injected into susceptible strains of mice. Since its discovery, this murine model of leukemogenesis has been extensively used to study the multistage nature of cancer. In the past two decades, several oncogenes and tumour suppressor genes, which play critical roles in the induction and progression of Friend erythroleukemia, have been identified. Retroviral insertional activation of Fli-1 and Spi-1/PU.1, as well as loss of tumour suppressor genes such as p53 or p45 NFE2 have been shown to be critical for the induction and progression of Friend virus-induced erythroleukemias. The majority of these genetic changes have also been implicated in various types of human neoplastic transformations. In this review we will discuss the genetic changes associated with Friend Disease, the temporal order during induction and progression of disease, and the function of these genes in both normal erythroid development as well as malignant transformation.
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PMID:Friend virus-induced erythroleukemias: a unique and well-defined mouse model for the development of leukemia. 1289 91

Controversy still exists over the response to therapy and prognosis of patients with primary mediastinal B-cell lymphoma (PMBL). Recent data from the International Extranodal Lymphoma Study Group (IELSG) suggest that a MACOP-B (methotrexate, adriamycin, cyclophosphamide, vincristine, prednisone, bleomycin) chemotherapy regimen followed by radiotherapy may be a better induction strategy than other previously used treatments. Although the pathobiology of PMBL has been widely studied, its precise histology, phenotype, and molecular characteristics are still not clear. To date, phenotypic analysis has revealed the following phenotype: positivity for CD45 and CD20, but negativity for CD3, CD10, CD21, Class I/II major histocompatibility antigens, and a variety of other immunohistochemical markers. CD79a is generally detected, despite an absence of surface immunoglobulins (Igs). CD30 staining is observed in most cases, but is weaker and less homogeneous than in classic Hodgkin's lymphoma or anaplastic large cell lymphoma. BCL-2 protein is usually expressed but there are few data describing the expression of MUM1/IRF4, PAX5/BSAP, BCL-6, or the B-cell transcription factors BOB.1, Oct-2, and PU.1. Cytogenetic studies reveal gains in segments of chromosome 9p, including amplification of the REL proto-oncogene and the tyrosine kinase gene JAK2. Other molecular findings include: C-myc mutations or rearrangements, p53 mutations, IgV(H), gene mutations, and bcl-2 and mal over-expression. bcl-6 mutations and bcl-2 gene rearrangements are generally absent, suggesting that PMBL is of pre-germinal center (GC) origin. However, two recent reports show isotype-switched Ig genes with a high frequency of somatic hypermutations as well as variants in the 5' noncoding region of the bcl-6 gene. The IELSG collected 137 PMBL cases for extensive pathologic review. Histologically, the lymphomatous growth was predominantly diffuse with sclerosis that induced compartmentalized cell aggregation. It consisted of large cells with varying degrees of nuclear polymorphism and clear to basophilic cytoplasm. Molecular analysis was performed on 40 cases and showed novel findings. More than half of the cases displayed bcl-6 gene mutations, which usually occurred together with functioning somatic IgV(H) gene mutations, and BCL-6 and/or MUM1/IRF4 expression. The present study supports the concept that PBML is derived from activated GC or post-germinal center cells. However, it differs from other aggressive B-cell lymphomas in that it shows defective Ig production despite the expression of Oct-2, BOB.1, and PU.1 transcription factors, and a lack of IgV(H) gene crippling mutations.
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PMID:Pathobiology of primary mediastinal B-cell lymphoma. 1520 21

Friend erythroleukemia virus has long served as a paradigm for the study of the multistage progression of leukemia. Friend virus infects erythroid progenitor cells, followed by an initial polyclonal expansion of infected cells, which is driven by the activation of a naturally occurring truncated form of the Stk receptor tyrosine kinase (Sf-Stk). Subsequently, the accumulation of additional mutations in p53 and the activation of PU.1 result in full leukemic transformation. The early stages of transformation induced by Friend virus are characterized in vitro by the Epo-independent growth of infected erythroblasts. We have shown previously that this transforming event requires the kinase activity and Grb2 binding site of Sf-Stk and the recruitment of a Grb2/Gab2 complex to Sf-Stk. Here, we demonstrate that Stat3 is required for the Epo-independent growth of Friend virus-infected cells and that the activation of Stat3 by Sf-Stk is mediated by a novel Stat3 binding site in Gab2. These results underscore a central role for Stat3 in hematopoietic transformation and describe a previously unidentified role for Gab2 in the recruitment and activation of Stat3 in response to transforming signals generated by tyrosine kinases.
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PMID:A novel Stat3 binding motif in Gab2 mediates transformation of primary hematopoietic cells by the Stk/Ron receptor tyrosine kinase in response to Friend virus infection. 1735 74

Accumulating evidences suggest that many molecules are working as inhibitors of proliferation in myeloma cells e.g., PTEN, mTOR(PI3-kinase signal molecules), p53, RB1, INK4 family and KIP/CIP family (cell cycle check point molecules), PF4 (inhibitor of angiogenesis). In this review, significance of these molecules in myeloma is summarized. Additionally, our finding of growth inhibitory effect by PU.1 is explained.
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PMID:[Molecular mechanisms inhibiting proliferation of myeloma cells]. 1806 60

The transcription factor PU.1 is essential for terminal myeloid differentiation, B- and T-cell development, erythropoiesis and hematopoietic stem cell maintenance. PU.1 functions as oncogene in Friend virus-induced erythroleukemia and as tumor suppressor in acute myeloid leukemias. Moreover, Friend virus-induced erythroleukemia requires maintenance of PU.1 expression and the disruption of p53 function greatly accelerates disease progression. It has been hypothesized that p53-mediated expression of the p21(Cip1) cell cycle inhibitor during differentiation of pre-erythroleukemia cells promotes selection against p53 function. In addition to the blockage of erythroblast differentiation provided by increased levels of PU.1, we propose that PU.1 alters p53 function. We demonstrate that PU.1 reduces the transcriptional activity of the p53 tumor suppressor family and thus inhibits activation of genes important for cell cycle regulation and apoptosis. Inhibition is mediated through binding of PU.1 to the DNA-binding and/or oligomerization domains of p53/p73 proteins. Lastly, knocking down endogenous PU.1 in p53 wild-type REH B-cell precursor leukemia cells leads to increased expression of the p53 target p21(Cip1).
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PMID:PU.1 binding to the p53 family of tumor suppressors impairs their transcriptional activity. 1819 90

Phagocytic clearance of apoptotic cells by macrophages is an essential part in the resolution of inflammation. It coincides with activation of repair mechanisms, including accumulation of extracellular matrix. A possible link between clearance of apoptotic debris and accumulation of extracellular matrix has not been investigated. Production of collagen was measured in primary fibroblasts cocultured with macrophages. Ingestion of apoptotic cells by monocyte-derived macrophages led to up-regulation of collagen. Direct contact between macrophages and fibroblasts was not required for collagen up-regulation. Macrophages produced TGF-beta following ingestion of apoptotic cells, but the levels of this cytokine were lower than those required for a significant up-regulation of collagen. Simultaneously, the levels of TGF-beta-induced (TGFBI), or keratoepithelin/BIGH3, mRNA and protein were increased. In contrast, primary alveolar macrophages stimulated collagen production without exposure to apoptotic cells; there was no further increase in the levels of TGFBI, mRNA or protein, or collagen after ingestion of apoptotic cells. Stimulation of fibroblasts with TGFBI down-regulated MMP14 levels, decreased DNA binding by p53, increased DNA binding by PU.1, and up-regulated collagen protein but not mRNA levels. Overexpression of MMP14 or p53, or small interfering RNA-mediated inhibition of PU.1 led to an increase in MMP14 and a decline in collagen levels, whereas small interfering RNA-mediated inhibition of MMP14 led to elevation of collagen levels. In conclusion, monocyte-derived but not alveolar macrophages produce TGFBI following ingestion of apoptotic cells, leading to the down-regulation of MMP14 levels in fibroblasts through a mechanism involving p53 and PU.1, and to subsequent accumulation of collagen.
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PMID:Macrophages produce TGF-beta-induced (beta-ig-h3) following ingestion of apoptotic cells and regulate MMP14 levels and collagen turnover in fibroblasts. 1835 29

Histone-modified enzymes are involved in various cell functions, including proliferation, differentiation, cell death and carcinogenesis. The protein MOZ (monocytic leukemia zinc finger protein) is a Myst (MOZ, Ybf2 (Sas3), Sas2, Tip60)-type histone acetyltranseferase (HAT) that generates fusion genes, such as MOZ-TIF2, MOZ-CBP and MOZ-p300, in acute myeloid leukemia (AML) by chromosomal translocation. MOZ associates with AML1 (RUNX1), PU.1, and p53, and cooperatively activates target gene transcription. Gene targeting in mice has revealed that MOZ is essential for the generation and maintenance of hematopoietic stem cells (HSC) and for the appropriate development of myeloid, erythroid and B-lineage cell progenitors. In AML, MOZ fusion genes lead to repressed differentiation, hyper-proliferation, and self-renewal of myeloid progenitors through deregulation of MOZ-regulated target gene expression. It is therefore necessary to analyze the roles of MOZ and MOZ fusion genes in normal and malignant hematopoiesis to elucidate the mechanisms underlying and develop therapies for MOZ-related AML.
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PMID:Roles of the histone acetyltransferase monocytic leukemia zinc finger protein in normal and malignant hematopoiesis. 1875 62


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