Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have shown that Tax1 of human T-cell leukemia virus type 1 stimulates the expression of several cellular immediate-early genes (M. Fujii, T. Niki, T. Mori, T. Matsuda, M. Matsui, N. Nomura, and M. Seiki, Oncogene 6:1023-1029, 1991). In this study, the 5'-flanking region of the human fra-1 gene, which is a Tax1-inducible fos-related gene, was isolated and Tax1 or serum-responsive cis elements were analyzed to obtain further insight into the mechanism of Tax1 action. The 62-bp sequence starting 46 nucleotides upstream from the translation initiation site showed 71% homology with the sequence surrounding the TATA box of the c-fos promoter. Regulatory motifs identified in the c-fos promoter, such as an Ets-binding site, E boxes, a CArG box, c-fos AP-1 sites, and two retinoblastoma control elements, were also found upstream of the c-fos homology region. A 502-bp fragment containing these motifs mediated transcriptional activation by Tax1 or by serum in a transient transfection assay. Three independent Tax1-responsive regions (TRRs) were identified, and mutations in each revealed that one of the retinoblastoma control elements in TRR1 and the c-fos AP-1 sites in TRR2 and TRR3 were essential for the activation. Although TRR2 contains a CArG box-like sequence, it was a weak binding site for p67SRF, if it bound at all, and was not required for activation. All three TRRs could also mediate the signals stimulated by serum. Thus, Tax1 appears to activate fra-1 gene expression by means of a part of the cellular machinery similar to that which mediates growth signals.
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PMID:Human T-cell leukemia virus type 1 Tax activates transcription of the human fra-1 gene through multiple cis elements responsive to transmembrane signals. 823 Apr 24

Protein kinase C (PKC)-activating phorbol esters are known to induce the expression of several genes in monocytic cells. As the effect of serine-threonine kinases, such as PKC, is often counteracted by specific protein phosphatases, we have now examined the role of phosphatases in the regulation of the phorbol ester (PMA)-induced interleukin-1 beta (IL-1 beta) gene expression in the THP-1 monocytic leukaemia cell line. Okadaic acid (OA) is a potent tumour promoter, the function of which is based on its activity to inhibit the serine/threonine specific phosphatases 1 and 2A (PP1 and PP2A, respectively). Thus, it mimicks or potentiates the action of PKC activators in several cell types. Our data demonstrate that alone OA induced a very weak expression of IL-1 beta mRNA, but it strongly enhanced the PMA-induced IL-1 beta expression. To analyse the site of action of OA, the cells were transiently transfected with a chloramphenicol acetyl transferase (CAT)-reporter plasmid containing the AP-1 binding site as the enhancer. Alone, OA was a weak inducer of CAT-activity in these cells, but again it strongly enhanced the PMA-induced response. Similar data were obtained with cells transfected with a reporter plasmid containing the PMA-responsive element (containing a putative AP-1 binding site) of the IL-1 beta gene. Thus, these data indicate that the PMA-induced AP-1 enhancer activity, which is required for the expression of the IL-1 beta gene, is controlled in these cells by PP1 and/or PP2A. As OA did not synergize with PMA in the induction of expression of genes encoding the AP-1 proteins (c-fos, c-jun, junB), it is likely that OA potentiates the AP-1 enhancer activity by its effect on protein phosphorylation.
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PMID:Okadaic acid, a phosphatase inhibitor, enhances the phorbol ester-induced interleukin-1 beta expression via an AP-1-mediated mechanism. 825 16

Sublines of K562 human leukemia cells were selected for resistance (30- to 80-fold) to etoposide by continuous exposure to 0.5 microM VP-16. Two etoposide-resistant cell lines, K/VP.5 and K/VP.5-1, showed a 5-fold reduction in levels of topoisomerase II alpha protein compared with K562 cells. Northern analysis indicated a 2.5-fold reduction in topoisomerase II alpha mRNA in etoposide-resistant cell lines, due in part to a 1.7-fold decrease in topoisomerase II mRNA stability with no change in transcription rate. Immunoblotting assays of electrophoresed cell lysates from VP-16-treated cells revealed less drug-induced covalent topoisomerase II/DNA adducts in resistant than in sensitive cells, suggesting a functional alteration in resistant cell topoisomerase II. Recent reports of specific topoisomerase II DNA binding sites near the promoter sites of growth response genes and alterations of gene expression in cells treated with topoisomerase II inhibitory drugs led to experiments to determine if the apparent functional alterations of topoisomerase II were accompanied by changes in the regulation of these genes. Therefore, the expression of several growth response genes was compared by northern analysis in parental K562 and both VP-16-resistant cell lines. Basal levels of c-myc were comparable for all three cell lines, but levels of c-jun and c-fos were elevated 2- to 4-fold in VP-16-resistant cell lines. Increased levels of c-fos and c-jun were not a result of altered rates of transcription, as determined by nuclear run-off assays. Exposure of both sensitive and resistant cells to 200 microM VP-16 for 5 hr resulted in no further changes in topoisomerase II mRNA levels but caused an additional 2- to 3-fold elevation in the level of c-jun mRNA, indicating that altered basal levels of this gene were not due to deregulation of this gene. Acquired VP-16 resistance in K/VP.5 and K/VP.5-1 cells was accompanied by reduced levels and altered activities of DNA topoisomerase II as well as changes affecting the expression of genes important for growth and differentiation.
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PMID:Altered gene expression in human leukemia K562 cells selected for resistance to etoposide. 826 50

Cross-linkage of the high-affinity receptor for IgE (Fc epsilon RI) by a polyvalent ligand, leads to activation of mast cells and basophils. We have studied Fc epsilon RI-mediated expression of RNA coding for the protooncogene, c-fos, in rat basophilic leukemia (RBL) cells and specifically have examined the requirements for ongoing receptor aggregation in the generation of this signal. RBL cells were sensitized with IgE specific for 2,4-dinitrophenyl (DNP) and incubated at 37 degrees C in the presence of DNP24BSA or BSA alone. Following activation for 0 to 30 min, the reaction was terminated. RNA was isolated and separated on denaturing gels, blotted to nylon membranes and hybridized with a 32P-labelled cDNA probe for c-fos. Messenger RNA for c-fos is detectable as early as 5-10 min following the addition of antigen and increases in a time-dependent fashion over 30 min. Unexpectedly, the addition of the hapten, 10(-4) M DNP-lysine, 5 min after the addition of antigen (which causes immediate cessation of exocytosis) does not dramatically alter the amount of message detected at 30 min. This effect is present as early as 2 min after cross-linking of the receptor and occurs at various doses of the aggregating stimulus. Thus, in contrast to the case with exocytosis and other well-described intracellular events, Fc epsilon RI-mediated increases in the level of mRNA for c-fos does not require ongoing aggregation of Fc epsilon RI.
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PMID:Fc epsilon RI-mediated expression of mRNA for c-fos in rat basophilic leukemia cells does not require ongoing aggregation of the receptor. 831 36

Granulocyte-macrophage colony-stimulating factor (GM-CSF) plays a critical role in growth and differentiation of myeloid cells. We previously reconstituted high affinity human GM-CSF receptor (hGM-CSFR) in a proB cell line BA/F3 by cotransfecting alpha and beta chain cDNA clones and showed that the reconstituted receptor could transduce growth promoting signals. The high affinity hGM-CSFR was also reconstituted in mouse NIH3T3 cells, but its ability to transduce signals in fibroblasts remained unanswered. In the present study, we further characterized signal transduction by the reconstituted hGM-CSFR both in NIH3T3 cells and BA/F3 cells. We found that the reconstituted hGM-CSFR transduces signals in NIH3T3 fibroblasts and BA/F3 cells in response to human GM-CSF to activate transcription of c-fos, c-jun and c-myc protooncogenes. hGM-CSF also induces protein tyrosine phosphorylation and DNA synthesis in both cell types. The ability of hGM-CSFR to transduce signals was affected by inhibitors of tyrosine kinase. These results indicated that the hGM-CSFR is functional in fibroblasts, that signal transduction via the hGM-CSFR in fibroblasts involves tyrosine kinase(s) and that association of hGM-CSFR with factor(s) specific to hematopoietic cell lineage is not essential to transduce growth promoting signals.
Leukemia 1993 Aug
PMID:Reconstitution of functional human GM-CSF receptor in mouse NIH3T3 fibroblasts and BA/F3 proB cells. 836 Dec 10

A transcriptional activator of human T-cell leukemia virus type 1 (HTLV-1) activates at least three distinct enhancers: the viral 21-bp enhancer, the NF-kappa B binding site of the IL-2R alpha gene and the CArG box of the c-fos gene. To understand the mechanisms of Tax transactivations of the NF-kappa B enhancer and CArG box, the interactions of Tax protein with their binding factors were analysed. Using a DNA affinity precipitation (DNAP) assay, we found here that Tax associates with the DNA sequences of the NF-kappa B site and CArG box. These Tax associations with enhancers were observed only in the presence of a nuclear factor(s) and were equal to the activating capacities of Tax mutants. To identify the nuclear factor(s), we defined conditions under which no Tax binding to the NF-kappa B binding site and CArG box was detected with a nuclear extract of 293T cells. Under these conditions, transfections with cDNAs of the NF-kappa B p50 and serum response factor (SRF) produced a factor(s) that mediated Tax binding to the NF-kappa B site and the CArG box respectively. Furthermore, purified Tax protein interacted with purified NF-kappa B p50 and purified SRF, indicating their direct bindings. These observations indicate that Tax protein associates with enhancer sequences of the NF-kappa B site and CArG box through NF-kappa B p50 and SRF respectively. Previously we demonstrated that Tax interacts with CREB and CREM proteins that bind to the 21-bp enhancer DNA. These results together suggest that indirect binding of Tax to DNA through each enhancer binding protein is a general mechanism for Tax transactivation of transcription.
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PMID:A trans-activator Tax of human T-cell leukemia virus type 1 binds to NF-kappa B p50 and serum response factor (SRF) and associates with enhancer DNAs of the NF-kappa B site and CArG box. 836 55

Spleen cells freshly isolated from normal mice were irradiated with 20 Gy X rays in culture. Northern blot hybridizations revealed that expression of the interleukin-1 beta (IL-1 beta) gene was induced immediately after irradiation and was increased for 2 h thereafter. Dibutyryl cyclic AMP also caused a persistent expression of the IL-1 beta gene, although it differed from X rays in that it coincidentally induced expression of the c-fos gene, which was not induced by X rays. Activation of either protein kinase C or calmodulin also induced early expression of both IL-1 beta and c-fos. Myeloid cells collected from the spleen of mice with granulocytic leukemia were X-irradiated in culture as above. The leukemia cells responded to X rays as well as to other stimuli in the same manner as the spleen cells, except that IL-1 beta mRNA was no longer detected 30 min after irradiation while c-fos was detectable for 2 h. When the leukemia cells were irradiated twice with a 3-h interval between irradiations, the second irradiation led to prolonged expression of IL-1 beta without inducing c-fos expression. These results suggest that ionizing radiation elicits early expression of the IL-1 beta gene through a mechanism that does not involve protein kinase C or A, or the transcription factor, c-fos. Whole-body irradiation of mice with 50 Gy 137Cs gamma rays also induced IL-1 beta expression in spleen but not in bone marrow or liver, although there was a delay of several hours before it was amply expressed. Furthermore, a delay as long as 24 or 72 h was observed when the radiation dose was reduced to 8.5 or 4 Gy. The results of this in vivo study suggest that the rapidity of expression of the IL-1 beta gene is dependent on the dose of radiation, and that the cells in the body cannot respond to radiation as rapidly as cells in culture.
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PMID:Induction of the expression of the interleukin-1 beta gene in mouse spleen by ionizing radiation. 838 62

Among various myeloid leukemias which were induced by X rays in C3H/He mice (Seki et al., Radiat. Res. 127, 146-149, 1991), the three most frequent types were analyzed for myeloperoxidase, c-myc, c-myb, and c-fos mRNAs. It was shown by in situ hybridization that all the component cells were positive for myeloperoxidase mRNA in granulocytic leukemia, whereas only half the cells were positive in myelomonocytic leukemia and none in monocytic leukemia. Granulocytic leukemia was also characterized by a persistently heightened expression of c-fos, while the other two types of leukemia showed negligibly low expression of the c-fos message. By contrast, both c-myc and c-myb were expressed to a similar extent in all three types of leukemia. When fresh granulocytic leukemia cells were transferred to culture in a medium containing 0.5% fetal calf serum, c-fos mRNA was decreased rapidly during incubation. The decay of c-fos mRNA was inhibited by cycloheximide markedly but was not changed significantly by actinomycin D. In the culture containing 10% fetal calf serum, the rate of decay of c-fos mRNA was slowed down significantly. Addition of dibutyryl cyclic AMP rapidly restored the c-fos expression and kept it elevated for at least 2 h in the cultured granulocytic leukemia cells. Phorbol ester (TPA) and calcium ionophore A23187 also caused a rapid but transient c-fos expression. A transient c-fos expression was inducible by TPA in the other two types of leukemia cells and in the granulocytic leukemia cells. The results suggest that the persistent expression of c-fos is distinguished from its transient expression and is characteristic for granulocytic leukemia cells as it is for normal mature granulocytes.
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PMID:Constitutive overexpression of the c-fos gene in radiation-induced granulocytic leukemia in mice. 839 29

The proto-oncogenes c-jun, junB, junD, and c-fos recently have been shown to encode for transcription factors with a leucine zipper that mediates dimerization to constitute active transcription factors; juns were shown to dimerize with each other and with c-fos, whereas fos was shown to dimerize only with juns. After birth, hematopoietic cells of the myeloid lineage, and some other terminally differentiated cell types, express high levels of c-fos. Still, the role of fos/jun transcription factors in normal myelopoiesis or in leukemogenesis has not been established. Recently, c-jun, junB, and junD were identified as myeloid differentiation primary response genes stably expressed following induction of terminal differentiation of myeloblastic leukemia M1 cells. Intriguingly, c-fos, though induced during normal myelopoiesis, was not induced upon M1 differentiation. To gain further insights into the role of fos/jun in normal myelopoiesis and leukemogenicity, M1fos and M1junB cell lines, which constitutively express c-fos and junB, respectively, were established. It was shown that enforced expression of c-fos, and to a lesser extent junB, in M1 cells results in both an increased propensity to differentiate and a reduction in the aggressiveness of the M1 leukemic phenotype. M1fos cells constitutively expressed immediate-early and late genetic markers of differentiated M1 cells. The in vitro differentiation of normal myeloblasts into mature macrophages and granulocytes, as well as the increased propensity of M1fos leukemic myeloblasts to be induced for terminal differentiation, was dramatically impaired with use of c-fos antisense oligomers in the culture media. Taken together, these observations show that the proto-oncogenes which encode for fos/jun transcription factors play important roles in promoting myeloid differentiation. The ability of the M1 leukemic myeloblasts to be induced for terminal differentiation in the absence of apparent fos expression indicates that there is some redundancy among the fos/jun family of transcription factors in promoting myeloid differentiation; however, juns alone cannot completely compensate for the lack of fos. Thus, genetic lesions affecting fos/jun expression may play a role in the development of "preleukemic" myelodysplastic syndromes and their further progression to leukemias.
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PMID:Proto-oncogenes of the fos/jun family of transcription factors are positive regulators of myeloid differentiation. 842 6

Recent evidence has established an important role for leukemia inhibitory factor (LIF) as hematopoietically active cytokine. The present study utilized two different murine bone marrow stromal cell lines, +/+-1.LDA11 and MBA-13, to define regulatory mechanisms of LIF messenger RNA (mRNA) induction. LIF mRNA was not detected in uninduced stromal cells under serum-free conditions. Incubation with interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-alpha) or the cAMP analogue 8-bromoadenosine 3':5'-monophosphate (8BrcAMP) resulted in weakly induced LIF mRNA. Coincubation of combinations of the stimuli increased LIF mRNA expression additively. LIF mRNA stability, even after stimulation, was low with a half-life of about 30 min, suggesting a functional role for known AU-rich motifs in the 3' untranslated LIF mRNA region in mediating this instability. This possibility was further supported by the ability of cycloheximide to increase mRNA levels without affecting transcription. Transcriptional activation was found to be the main mechanism leading to LIF mRNA expression by IL-1, by TNF-alpha, and by 8BrcAMP. These stimuli appeared to act additively in this regard, suggesting involvement of distinct transcription factors. Induction of transcription was detected 45 min post-stimulation and showed peak levels at 90 min. Kinetics of LIF transcriptional activation showed similarity with the kinetics of the transcription factors, jun-B and c-fos, suggesting a possible role for these proteins or other early response genes in events leading to LIF expression.
Leukemia 1993 Apr
PMID:LIF mRNA expression is transcriptionally regulated in murine bone marrow stromal cells. 846 40


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