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Query: UMLS:C0023418 (leukemia)
 93,477 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The synthesis of core histone variants and of histone H1 variants was determined in fresh leukemic cells of eight patients with leukemia [seven acute lymphoblastic (ALL) and one chronic lymphocytic (CLL)], in normal lymphocytes from healthy donors or from ALL patients in complete remission. Histone variant synthesis was evaluated by incubating cells with [14C]Lys and [3H]Arg in medium without Lys and Arg and then by two-dimensional polyacrylamide gel electrophoretic separations (acetic acid-urea-Triton x-100 acetic acid-urea-hexadecyltrimethylammonium bromide for core histone variants; sodium dodecyl sulfate/acetic acid-urea-hexadecyltrimethyl ammonium bromide for H1 variants). As previously reported, quiescent lymphocytes and lymphocytes stimulated with phytohaemagglutinin (PHA) showed clearcut changes in the proportions of synthesis of core histone variants and H1 variants. Leukemic lymphocytes freshly obtained from blood showed a pattern of core histone synthesis and H1 synthesis intermediate between that of quiescent and PHA-stimulated lymphocytes; this is probably due to the presence of a mixture of resting and growing cells. When leukemic cells were stimulated to grow by mitogens, the pattern of core histone and H1 variant synthesis was similar to that in mitogen-stimulated normal lymphocytes. Histone variants whose synthesis is associated with the S-phase were not synthesized in leukemic cells treated with the DNA synthesis inhibitors hydroxyurea and 1-beta-D-arabinofuranosylcytosine (Ara-C). The pattern of acetylation of histone H4 was also apparently similar in leukemic cells and normal lymphocytes. The radioactivity associated with the ubiquitinated forms of H2A increased in nongrowing lymphocytes and in leukemic cells treated with DNA synthesis inhibitors whereas they decreased after mitogenic stimulation. Variability was wide in the synthesis of ubiquitinated H2A in different cases of leukemia. The only clear-cut difference between leukemic cells and normal lymphocytes was that leukemic cells from ALL patients, but not lymphocytes from normal donors or from ALL patients in complete remission, synthesized appreciable amounts of H1 degrees, increasing after hydroxyurea/Ara-C treatment and decreasing after PHA-stimulation. In leukemic cells from a CLL patient H1 degrees synthesis was undetectable.
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PMID:Comparison of histone variant synthesis in human lymphocytic leukemia cells and in normal lymphocytes. 283 21

Using [32P]histone as substrate, an assay for histone phosphate phosphatase was optimised for human polymorphonuclear leukocytes. Kinetic studies showed that the activity was optimal at pH 6.8, was stimulated by Mn2+ and Co2+, and inhibited by sodium sulphite and zinc chloride. The apparent Km of the enzyme for histone phosphate was 0.89 mumol/l. Neutrophils were homogenized in isotonic sucrose and, after low speed centrifugation, the supernatant was subjected to analytical subcellular fractionation. Gradient fractions were assayed for principal marker enzymes and for histone phosphate phosphatase. Histone phosphate phosphatase activity was shown to be solely located to the cytosol. No activity was detected in the alkaline phosphatase-containing granules. Neutrophils were isolated from the blood of control subjects, patients with chronic granulocytic leukaemia and women in the third trimester of pregnancy. The specific activity (milliunits/mg protein) of histone phosphate phosphatase was significantly reduced in patients with chronic granulocytic leukaemia compared to control values but this decrease was considerably less than that found for alkaline phosphatase. The possible implication of the reduced histone phosphatase activity in leukaemia neutrophils is discussed. There was no significant change in histone phosphate phosphatase in leucocytes from pregnant women. These results, together with the subcellular fractionation experiments and inhibitor studies, strongly indicate that histone phosphate phosphatase is not attributable to neutrophil alkaline phosphatase.
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PMID:Subcellular localisation and properties of histone phosphate phosphatase in human polymorphonuclear leukocytes: alterations in pregnancy and chronic granulocytic leukaemia and relationship to alkaline phosphatase. 693 12

Histone acetylation modifiers have been described to participate as cofactors in mammalian transcriptional complexes involved in the regulation of cellular proliferation and differentiation. The acetylation of core histone proteins is reversible and regulated by two competing enzymatic activities, histone acetyltransferases (HATs) and histone deacetylases (HDACs). Increasing evidence suggests a connection between histone acetylation and the development of cancer and leukemia. We have recently mapped HDAC3 to mouse chromosome 18B3, a region which is syntenic with human chromosome 5q31, where HDAC3 is imbedded in a group of potential tumor suppressor genes and which has been reported to be the smallest commonly deleted segment in malignant myeloid disease. We report herein the identification and characterization of HDAC3, a yeast RPD3 ortholog in the mouse. Studies on murine HDAC3 may yield important insights on the understanding of myeloproliferative disease in humans.
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PMID:Cloning and characterization of the murine histone deacetylase (HDAC3). 1049 19

Histone deacetylases (HDACs) are a growing family of enzymes implicated in transcriptional regulation by affecting the acetylation state of core histones in the nucleus of cells. HDACs are known to have key roles in the regulation of cell proliferation [Brehm, Miska, McCance, Reid, Bannister and Kouzarides (1998) Nature (London) 391, 597-600], and aberrant recruitment of an HDAC complex has been shown to be a key step in the mechanism of cell transformation in acute promyelocytic leukaemia [Grignani, De Matteis, Nervi, Tomassoni, Gelmetti, Cioce, Fanelli, Ruthardt, Ferrara, Zamir et al. (1998) Nature (London) 391, 815-818; Lin, Nagy, Inoue, Shao, Miller and Evans (1998), Nature (London) 391, 811-814]. Here we present the complete nucleotide sequence of a cDNA clone, termed HDAC8, that encodes a protein product with similarity to the RPD3 class (I) of HDACs. The predicted 377-residue HDAC8 product contains a shorter C-terminal extension relative to other members of its class. After expression in two cell systems, immunopurified HDAC8 is shown to possess trichostatin A- and sodium butyrate-inhibitable HDAC activity on histone H4 peptide substrates as well as on core histones. Expression profiling reveals the expression of HDAC8 to various degrees in every tissue tested and also in several tumour lines. Mutation of two adjacent histidine residues within the predicted active site severely decreases activity, confirming these residues as important for HDAC8 enzyme activity. Finally, linkage analysis after radiation hybrid mapping has localized HDAC8 to chromosomal position Xq21.2-Xq21.3. These results confirm HDAC8 as a new member of the HDAC family.
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PMID:Cloning and characterization of a novel human histone deacetylase, HDAC8. 1092 44

Histone deacetylases are promising targets for cancer treatment. Here we studied the in vitro effects of a potent histone deacetylase inhibitor, FK228 (formerly FR901228), on human leukemia / lymphoma cells and cell lines compared with normal hematopoietic cells. In a lymphoma cell line, Raji, a nanomolar concentration of FK228 induced G1 arrest and / or apoptotic cell death, depending on the concentration and exposure time. Growth of lymphoid cell lines including Raji (N = 13) was inhibited by 50% (IC(50)) after 2-day treatment at concentrations of 0.83 to 1.87 ng / ml. Viability of clinical samples from patients with acute lymphoblastic leukemia was decreased by 50% at 0.78 +/- 0.46 ng / ml, whereas the IC(50) values for normal mononuclear cells from peripheral blood and bone marrow were 2.3 +/- 0.96 and 7.8 +/- 1.0 ng / ml, respectively. The IC(50) values for normal progenitor cells were 3.1, 4.4 and 7.8 ng / ml for BFU-E, CFU-GM and CFU-Mix, respectively. Expression levels of HDAC-1 and HDAC-3 proteins, which varied among cell lines, but were stable during the treatment with FK228, did not correlate with the sensitivity to FK288. This novel agent might be useful in the treatment of lymphoid malignancies, because the above concentrations are clinically achievable in vivo according to a recent clinical study.
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PMID:Apoptotic cytotoxic effects of a histone deacetylase inhibitor, FK228, on malignant lymphoid cells. 1109 81

Histone acetylation and deacetylation are closely linked to transcriptional activation and repression, respectively. In acute promyelocytic leukemia (APL), histone deacetylase inhibitors (HDACIs) have a synergistic effect with all-trans retinoic acid (ATRA) in vitro to induce differentiation. Here we report in vitro and in vivo effects of a HDACI, FK228 (formerly FR901228 or depsipeptide), on the human APL cell line NB4. FK228 had a strong and irreversible cytotoxicity compared with another HDACI, trichostatin A. In vivo administration of ATRA or FK228 alone partly inhibited the growth of established tumors of NB4 subcutaneously transplanted in NOD / Shi-scid / scid mice, and the combination was synergistically effective. Histopathological examination revealed that the combination induced apoptosis and differentiation as well as histone acetylation. Intravenous injection of NB4 in NOD / Shi-scid / scid mice followed by combination treatment significantly prevented leukemia death, whereas single administration did not. These findings suggest that FK228 is a promising agent to enhance ATRA-sensitivity in the treatment of APL.
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PMID:In vivo effects of a histone deacetylase inhibitor, FK228, on human acute promyelocytic leukemia in NOD / Shi-scid/scid mice. 1137 62

Histone deacetyrase (HDAC) inhibitors induce growth arrest and differentiation of leukemia cell lines and tumor cells derived from a large variety of human tissues. Here we showed that HDAC inhibitors sodium butyrate, TSA, and valproate regulated the expression of Interleukin-18 (IL-18), a cytokine with antitumor and proinflammatory properties, in human acute myeloid leukemia cell lines U937 and HEL. Sodium butyrate increased expression of IL-18 protein and mRNA and activated 1357bp IL-18 gene promoter construct. IL-18 mRNA level was up-regulated by TSA or valproate, which also activated IL-18 full-length promoter. While sodium butyrate or TSA stimulated the 108-bp IL-18 minimal promoter, valproate failed to activate it, indicating that valproate may use a distinct mechanism from sodium butyrate and TSA to activate IL-18 gene expression.
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PMID:Differential effects of histone deacetylase inhibitors on interleukin-18 gene expression in myeloid cells. 1194 5

Histone acetyltransferases (HATs) and histone deacetylases (HDACs) are known to interact with several transcription factors and regulate their transcriptional activities. The human T-cell leukemia virus type 1 (HTLV-1) Tax oncoprotein activates transcription from its long terminal repeat (LTR) through interaction with cellular factors such as CREB and a transcriptional coactivator CBP/p300. However, little is known about the interaction between Tax and transcriptional repressors. Here, we demonstrate the physical and functional interaction between Tax and HDAC1. We found that HDAC1 represses the trans-activation function of Tax in 293T and MT4 cells. However, this repression was restored by treatment with an HDAC inhibitor, Trichostatin A. We also observed physical interaction between Tax and HDAC1 both in vitro and in vivo. The N-terminal region of HDAC1 (amino acid residues 28-97) was required for this binding. Moreover, HDAC1 inhibited the synergistic trans-activation of Tax observed on ectopic expression of CBP. However, this repression was relieved by overexpression of CBP. Thus, HDAC1 is likely to compete with CBP in binding with Tax and functions as a negative regulator for the transcriptional activation by Tax.
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PMID:The interaction of HTLV-1 Tax with HDAC1 negatively regulates the viral gene expression. 1237 Aug 15

The human T-cell leukemia virus (HTLV-I)-encoded Tax protein is a potent transcriptional activator that stimulates expression of the integrated provirus. Biochemical studies indicate that Tax, together with cellular transcription factors, interacts with viral cAMP-response element enhancer elements to recruit the pleiotropic coactivators CREB-binding protein and p300. Histone acetylation by these coactivators has been shown to play a major role in activating HTLV-I transcription from chromatin templates in vitro. However, the extent of histone modification and the precise identity of the cellular regulatory proteins bound at the HTLV-I promoter in vivo is not known. Chromatin immunoprecipitation analysis was used to investigate factor binding and histone modification at the integrated HTLV-I provirus in infected T-cells (SLB-1). These studies reveal the presence of Tax, a variety of ATF/CREB and AP-1 family members (CREB, CREB-2, ATF-1, ATF-2, c-Fos, and c-Jun), and both p300 and CREB-binding protein at the HTLV-I promoter. Consistent with the binding of these coactivators, we observed histone H3 and H4 acetylation at three regions within the proviral genome. Histone deacetylases were also present at the viral promoter and, following their inhibition, we observe an increase in histone H4 acetylation on the HTLV-I promoter and a concomitant increase in viral RNA. Together, these results suggest that a variety of transcriptional activators, coactivators, and histone deacetylases participate in the regulation of HTLV-I transcription in infected T-cells.
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PMID:Transcription factor binding and histone modifications on the integrated proviral promoter in human T-cell leukemia virus-I-infected T-cells. 1238 57

Histone acetylation is one major mechanism by which chromatin structure and function are regulated. Besides histones, many nonhistone proteins are also acetylated in vivo. Aberrant acetylation has been linked to the development of various human diseases. Through acetylating histone and nonhistone proteins, histone acetyltransferases (HATs) play fundamental roles in regulating chromatin remodeling, transcription, and other nuclear processes. Known HATs belong to several groups, including the GCN5/PCAF, p300/CBP, and MYST families. ESA1, SAS3, MOF, TIP60, HBO1, MOZ, and MORF are the MYST family members with demonstrated HAT activity. The MOZ and MORF genes are rearranged by chromosome abnormalities associated with several types of leukemia, so these two HATs have been implicated in leukemogenesis. Compared with p300, CBP, and PCAF, much less is known about MOZ and MORF. To elucidate the function and regulation of these two interesting HATs, we have conducted their initial characterization. Here we describe the expression, purification, and activity analysis of MOZ and MORF. For comparison, we also include the procedure for expression and purification of PCAF. These methods are useful not only for functional characterization of MOZ, MORF, PCAF, and other HATs, but also for preparation of HAT proteins to screen compound libraries and obtain inhibitors with potential therapeutic value.
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PMID:Expression, purification, and analysis of MOZ and MORF histone acetyltransferases. 1289 70


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