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

Feline leukemia virus DNA polymerase was purified by ion-exchange and nucleic acid affinity chromatographies. The enzyme consists of a single polypeptide chain of mol. wt. approx. 72,000 as determined by both glycerol density gradient centrifugation and SDS-polyacrylamide gel electrophoresis. The preferred divalent cation for DNA synthesis is Mn2+ on a variety of template-primers, and its optimum concentration appears to be significantly lower than reported results of other mammalian type-C viral enzymes. The purified enzyme also contained RNAase H activity. Both DNA polymerase and RNAase H activities appear to reside on the same molecule as demonstrated by the copurification of both activities through various purification steps. The divalent cation requirement for maximum activity of RNAase H is also similar to that of the DNA polymerase. RNAase H without detectable polymerase activity was generated by a limited chymotrypsin digestion of the purified reverse transcriptase. This RNAase H activity was inhibited equally effectively as RNAase H in the intact reverse transcriptase by antisera prepared against reverse transcriptase of feline leukemia virus. These results indicate that the RNAase H catalytic activity of reverse transcriptase is distinct from the polymerase portion of the molecule. Since the RNAase H activity appears to be more stable, the measurement of RNAase H activity with a proper antibody might be useful for assaying tumor cells for the presence of the viral enzyme.
 ...
PMID:Biochemical and immunological properties of the DNA polymerase and RNAase H activities of purified feline leukemia virus reverse transcriptase. 615 69

Hybridoma antibodies directed against the Fc and Fab portions of rat IgE were produced by immunizing BALB/c mice with rat IgE and fusing the spleen cells with the nonsecreting plasmacytoma P3/X63Ag8.653. Two of the antibodies, designated as A2 and B5, were extensively characterized. Competitive binding experiments using rat IgE from the IR 162 and IR2 immunocytomas and rat IgG indicated that both A2 and B5 were epsilon-chain specific and not anti-idiotype. A2 also exhibited some cross-reactivity with mouse IgE. When IgE was treated with chymotrypsin so as to produce both F(ab')2 and Fab fragments, the enzyme-treated IgE retained reactivity with B5, but the reactivity to A2 was lost. Heat denaturation of IgE at 56 degrees C resulted in a progressive loss of reactivity of the IgE for both A2 and the Fc receptor on rat basophilic leukemia cells; the reactivity of B5 remained unchanged. A2 does not evidently interact with the same site on the Fc of IgE that is involved in binding to the rat basophilic leukemia cell Fc receptor; A2 exerted little influence on the binding of IgE to rat basophilic leukemia cells. Thus, the data indicate that the antigenic site for B5 is in the Fab region of the IgE molecule and that A2 reacts with the IgE Fc. Use of these antibodies to measure cell-bound IgE was also evaluated in dual label experiments, and potential problems in using divalent antibodies to quantitate cell surface antigens are discussed.
 ...
PMID:Properties of two monoclonal antibodies directed against the Fc and Fab' regions of rat IgE. 618 12

Partially purified IgE receptor(s) of rat basophilic leukemia cells (RBL) designated R and H and having apparent molecular weight of 45,000 and 55,000 daltons, respectively, were subjected to proteolysis with papain. Polyacrylamide gel electrophoresis of the digests in the presence of sodium dodecyl sulfate revealed a difference in the size and number of the fragments produced. These results suggest that these two receptor molecules are different with respect to amino acid composition and sequence. Whole Nonidet P-40 extracts of RBL cells were also subjected to digestions with papain, trypsin and chymotrypsin in an attempt to obtain receptor fragments still capable of binding to IgE-Sepharose. Treatment with papain produced a 38,000 dalton fragment of H but no fragments of R which retained the ability to bind to IgE. Tryptic and chymotryptic treatment produced a 41,000 dalton fragment of H with affinity for IgE. The IgE-binding site of R was either destroyed or not affected at all.
 ...
PMID:Proteolytic fragments of the receptors for IgE. 621 Jun 30

Leukemia-associated inhibitory activity suppresses colony and cluster formation in vitro cells derived from granulocyte-macrophage progenitor cells of normal donors. It does not inhibit these same progenitor cells from patients with leukemia and it may contribute to the proliferative advantage leukemia cells appear to possess over normal hematopoietic cells during acute leukemia. The inhibitory activity was isolated by a combination of procedures including: ultracentrifugation, Sephadex G-200, carboxymethylcellulose, SDS-polyacrylamide gel electrophoresis, thin-layer and preparative isoelectric focusing and concanavalin A-Sepharose. Leukemia-associated inhibitory activity was characterized as a glycoprotein. it was inactivated by trypsin, chymotrypsin, pronase and periodate treatment. It bound to and was eluted by alpha-methylmannose from concanavalin A-Sepharose columns and had an apparent Mr range of 450-550 000 and an isoelectric focus value between pH 4.6 and 4.9. Crude leukemia associated inhibitory activity was temperature sensitive but the more purified preparations were heat stable.
 ...
PMID:Isolation and biochemical characterization of leukemia-associated inhibitory activity that suppresses colony and cluster formation of cells. 697 52

Acidic isoferritins have been identified as leukemia-associated inhibitory activity (LIA), which suppresses colony and cluster formation of colony-forming unit-granulocyte macrophages from normal donors but not from patients with leukemia. LIA was detected in all ferritin preparations tested, including ferritin isolated from normal heart, spleen, liver, and placental tissues, and from the spleens of patients with chronic myelogenous leukemia and Hodgkin's disease. Purified preparations of LIA were composed almost entirely of acidic isoferritins, as determined by immunoassay, radioimmunoassay, and isoelectric focusing. The inhibitory activity in the LIA and ferritin samples was inactivated by a battery of antisera specific for ferritin, including those prepared against acidic isoferritins from normal heart and spleen tissues from patients with Hodgkin's disease, and those previously absorbed with basic isoferritins. Antisera absorbed with acidic isoferritins did not inactivate the inhibitory activity. Separation of LIA and chronic myelogenous leukemia and normal spleen ferritin by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and isoelectric focusing confirmed that the regions of peak inhibitory activity corresponded in each to an apparent molecular weight of approximately 550,000 and to a pI value of 4.7. Similar physicochemical characteristics included inactivation by methods that dissociate ferritin molecules into subunits and by treatment with trypsin, chymotrypsin, pronase, and periodate. The purified preparations were extremely stable to heat treatment. The glycoprotein nature of the inhibitory activity was substantiated because it bound to concanavalin A-Sepharose and was eluted off by alpha-methyl mannose. Inhibitory activity of the activity of the acidic isoferritins was detected at concentrations as low as 10(-17)-10(-19) M and iron saturation did not appear to be necessary for its action. These results implicate acidic isoferritins in the regulation of normal myelopoiesis and suggest a role for them in the progression of leukemia.
 ...
PMID:Identification of leukemia-associated inhibitory activity as acidic isoferritins. A regulatory role for acidic isoferritins in the production of granulocytes and macrophages. 697 99

A murine monoclonal antibody (mAb i3A; IgG1, kappa light chain) was obtained using human red blood cells as immunogen. The antibody showed Fy6 specificity since it agglutinated all but Fy(a-b-)-untreated red cells and failed to agglutinate chymotrypsin-treated cells. An erythrocyte membrane protein of 42-46 kD was revealed as the major component recognized by the antibody on immunoblots. The antibody also bound to 92- to 95- and 200-kD proteins, tentatively identified as oligomers of the 42- to 46-kD monomeric form. The affinity-purified Fy6-active protein was converted to a sharp band of 35 kD after N-glycanase treatment. The molecule appeared as a slightly broadly band after neuraminidase treatment but was not further altered by O-glycanase. The i3A mAb bound to 6,000 +/- 1,000 receptor sites on either Fy(a-b+), Fy (a+b+) and Fy(a+b-) red cells with an affinity constant in the range of 3-6 x 10(8) M-1. No binding was observed to other blood cells nor to several cells (B, T, myelomonocytic and erythro-leukemia cell lines). Also, the bulk of i3A-Fy6 immune complexes could be dissociated from the red cell membrane with as low as 0.2% Triton X-100, showing that the Fy6-active glycoprotein is not tightly associated with the membrane skeleton. Our data obtained with a new monoclonal antibody directed to the Fy6 antigen demonstrate that the blood group Duffy-active component is a red cell-specific glycoprotein carrying one or more N-linked oligosaccharides.
 ...
PMID:Production of a new murine monoclonal antibody with Fy6 specificity and characterization of the immunopurified N-glycosylated Duffy-active molecule. 814 85

We studied the role of proteases in apoptosis using a cell-free system prepared from a human leukemia cell line. HL60 cells are p53 null and extremely sensitive to a variety of apoptotic stimuli including DNA damage induced by the topoisomerase I inhibitor, camptothecin. We measured DNA fragmentation induced in isolated nuclei by cytosolic extracts using a filter elution assay. Cytosol from camptothecin-treated HL60 cells induced internucleosomal DNA fragmentation in nuclei from untreated cells. This fragmentation was suppressed by serine protease inhibitors. Serine proteases (trypsin, endoproteinase Glu-C, chymotrypsin A, and proteinase K) and papain by themselves induced DNA fragmentation in naive nuclei. This effect was enhanced in the presence of cytosol from untreated cells. Cysteine protease inhibitors (E-64, leupeptin, Ac-YVAD-CHO [ICE inhibitor]) did not affect camptothecin-induced DNA fragmentation. The apopain/Yama inhibitor, Ac-DEVD-CHO, and the proteasome inhibitor, MG-132, were also inactive both in the cell-free system and in whole cells. Interleukin-1 beta converting enzyme (ICE) or human immunodeficiency virus protease failed to induce DNA fragmentation in naive nuclei. Together, these results suggest that DNA damage activates serine protease(s) which in turn activate(s) nuclear endonuclease(s) during apoptosis in HL60 cells.
 ...
PMID:DNA fragmentation induced by protease activation in p53-null human leukemia HL60 cells undergoing apoptosis following treatment with the topoisomerase I inhibitor camptothecin: cell-free system studies. 880 33

A cytotoxic factor (CF) toward cultured murine leukemia L1210 cells was induced in mouse serum by intravenous injection of a dehydrogenation polymer of p-coumaric acid (DHP-pCA). When the serum from the treated mice was diluted with ethanol, CF was preserved in its supernatant (EtOH-sup). An EtOH-sup prepared from untreated control mice also showed cytotoxicity, although at much higher concentrations. The CF activity of EtOH-sups from both treated and untreated mice was completely eliminated by acid treatment at pH 2 at 90 degrees C for 30 min but kept intact by alkali treatment. In addition, the CF activity of both EtOH-sups was not affected by digestion with chymotrypsin. CF was recovered in a neutral MeOH-eluate from a DEAE-cellulofine column but not in HCI-MeOH eluate, in which lignified materials including DHP-pCA should have been recovered. These findings strongly suggest that CF is not a metabolite of DHP-pCA but an endogenous component of the normal serum which is augmented by DHP-pCA administration.
 ...
PMID:Cytotoxic factor induced in murine serum after intravenous administration of a dehydrogenation polymer of p-coumaric acid (a synthetic lignin). 982 18

We examined the antileukemic activity and the toxicity of HPC transduced with human tumor necrosis factor (TNF) cDNA. Both clonal (32Dcl3) and BM-derived primary hematopoietic progenitors (BM-Prog) expressing hTNF-alpha gene (32DTNF-alpha and BMTNF-alpha cells, respectively) inhibited the development of leukemia in mice with a small dose of 32Dp210 cells, a myeloid leukemia cell line. Whether the trans-gene expressing 32DTNF-alpha cells produce toxicities commonly associated with systemic TNF-alpha therapy was determined by examining the effect of TNF-alpha-secreting progenitor cells on body weight, tissue histology, growth of HPC, and engraftment of BMT. Administration of a low or high dose of TNF-alpha-secreting 32DTNF-alpha cells to mice failed to produce loss in body weight, a measure of TNF-alpha-related cachexia. There was also no evidence of tissue necrosis or mononuclear cell (MNC) infiltration in lung, liver, kidney, or intestine of mice injected with transduced progenitor cells. Furthermore, 32DTNF-alpha cells showed no effect on the clonal growth of HPC in colony-forming assays or loss of cellularity in BM, spleen, or blood. Finally, TNF-alpha-secreting cells were found not to interfere with the engraftment of BM transplant and hematopoietic reconstitution thereafter. We conclude from these findings that unlike systemic administration of TNF-alpha, TNF-alpha gene therapy with transduced HPC is nontoxic and may have a role in eradicating residual leukemia after BMT.
 ...
PMID:TNF-alpha gene therapy with myeloid progenitor cells lacks the toxicities of systemic TNF-alpha therapy. 1041 46

To investigate the structural context of the fusion peptide region in human T-cell leukemia virus type 1 gp21, maltose-binding protein (MBP) was used as an N-terminal solubilization partner for the entire gp21 ectodomain (residues 313-445) and C-terminally truncated ectodomain fragments. The bacterial expression of the MBP/gp21 chimeras resulted in soluble trimers containing intramonomer disulfide bonds. Detergents blocked the proteolytic cleavage of fusion peptide residues in the MBP/gp21-(313-425) chimera, indicating that the fusion peptide is available for interaction with detergent despite the presence of an N-terminal MBP domain. Limited proteolysis experiments indicated that the transmembrane domain proximal sequence Thr(425)-Ala(439) protects fusion peptide residues from chymotrypsin. MBP/gp21 chimera stability therefore depends on a functional interaction between N-terminal and transmembrane domain proximal regions in a gp21 helical hairpin structure. In addition, thermal aggregation experiments indicated that the Thr(425)-Ser(436) sequence confers stability to the fusion peptide-containing MBP/gp21 chimeras. The functional role of the transmembrane domain proximal sequence was assessed by alanine-scanning mutagenesis of the full-length envelope glycoprotein, with 11 of 12 single alanine substitutions resulting in 1.5- to 4.5-fold enhancements in cell-cell fusion activity. By contrast, single alanine substitutions in MBP/gp21 did not significantly alter chimera stability, indicating that multiple residues within the transmembrane domain proximal region and the fusion peptide and adjacent glycine-rich segment contribute to stability, thereby mitigating the potential effects of the substitutions. The fusion-enhancing effects of the substitutions are therefore likely to be caused by alteration of the prefusion complex. Our observations suggest that the function of the transmembrane domain proximal sequence in the prefusion envelope glycoprotein is distinct from its role in stabilizing the fusion peptide region in the fusion-activated helical hairpin conformation of gp21.
 ...
PMID:Evidence that the transmembrane domain proximal region of the human T-cell leukemia virus type 1 fusion glycoprotein gp21 has distinct roles in the prefusion and fusion-activated states. 1159 47


<< Previous 1 2 3 4 5 6 Next >>