Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.7.7.7 (DNA polymerase)
17,007 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Terminal deoxynucleotidyl transferase (TDT) is an unusual DNA polymerase that does not use template information to synthesize new strands of DNA. It is normally found in high concentration in thymus (50 u/10(8) cells) and in low concentration in bone marrow (less than 5 u/10(8)). We report TDT measurements in the marrow and/or peripheral blood of 51 adult patients, 28 of whom had leukaemia. TDT is present in very high levels (greater than 50 u/10(8) cells) in leukaemic lymphoblasts and in low levels in leukaemic myeloblasts (less than 9 u/10(8) cells). Of two patients who developed lymphosarcoma-cell leukaemia following treatment of poorly differentiated lymphocytic lymphoma, one had high and one low levels of TDT in the leukaemic blast cells. Leukaemic cells from three of seven patients with chronic myeloid leukaemia in blast crisis had TDT levels within the range expected of acute lymphoblastic rather than acute myeloid leukaemia. High TDT in leukaemic cells probably marks them as derivatives of lymphoid progenitor, thymic or pluripotential stem cells. Quantitative assay of TDT may provide information useful in classifying haematological neoplasms.
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PMID:Terminal deoxynucleotidyl transferase measurements in the differential diagnosis of adult leukaemias. 6 84

Extracellular particles, with a density of 1.18-1.22 g/cm3 in sucrose, were detected in the culture medium of a continuous cell line (JIII) derived from a patient with monocytic leukemia. These particles contained RNA, DNA, and a DNA polymerase. They synthesized DNA with endogenous templates and primers and also used exogenous DNA but not poly(rC) oligo(dG) as a template. Pretreatment with Nonidet P-40 stimulated DNA polymerase activity while treatment with ribonuclease partially inhibited the enzyme activity. Fluorescent antibodies made to the particles stained both JIII and Z-597 cells derived from human leukemias but not other types of human or nonhuman cultured cells tested. The particles do not appear to be oncornaviruses but may be a particulate antigen associated with malignant cells of hemopoietic and lymphoid origin.
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PMID:Characterization of extracellular particles released from continuous cell cultures derived from human leukemia. 18 75

The present paper reports on the induction of two cell surface markers on human lymphoid cells following herpes simplex virus (HSV) infection. While both primary and chronic infections of human lymphoid cells led to the induction of receptors for the Fc region of 7S IgG, chronic HSV infection was also characterized by the induction of surface-bound IgM. Surface and intracellular Fc receptors were detected in the human lymphoid cell line, Raji, infected with HSV types 1 and 2. Under optimal conditions with a multiplicity of infection (m.o.i.) of 50 to 100 p.f.u. per cell, this marker was inducible in only about 53% of the infected cells. Kinetic studies revealed the appearance of these receptors at around 5 h following HSV infection and they reached a plateau 16 to 18 h p.i. Interestingly, this Fc receptor expression (i.e. percentage of positive cells) was found to be similar in primary and chronically HSV-infected Raji cells. Both human leukocyte interferon and phosphonoacetic acid (PAA), an inhibitor of herpesvirus DNA polymerase activity, effectively inhibited Fc receptor synthesis during primary HSV-infection and these two agents suppressed its induction in chronically HSV-infected Raji (Raji-HSV) cells. This inhibitory or suppressive effect, particularly of PAA, suggests that this HSV-induced Fc receptor may represent a late virus function in the infected cell. Unlike primary HSV infection, about 80% of the chronically HSV-infected Raji cells were found to express surface-bound IgM. This IgM induction was suppressed by long-term interferon treatment but not with PAA-treatment. Superinfection studies of interferon and PAA-treated Raji-HSV cells indicate that only the former would develop Fc receptors suggesting a protective role of this IgM against superinfection by HSV.
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PMID:Studies on the induction of IgG-Fc receptors and synthesis of IgM in primary and chronically-infected lymphoid (Raji) cells by herpes simplex virus. 23 Feb 88

Pituitary growth hormone (GH) has considerable potential as an anabolic agent in animal production. For example, pigs treated with GH will grow faster (i.e. deposit protein), require less feed per unit of body weight gain, and will have less carcass fat than untreated animals. Lactating cows will produce more milk with less feed. It is likely, though not completely established, that young cattle will also respond to GH treatments. Most of the information on the mode of action of GH has been obtained with laboratory rather than farm animals. The hormone affects almost all aspects of metabolism although the specific mechanism for these effects is still not understood. Stimulation of protein accretion is reflected by increased nitrogen retention and incorporation of radioactive amino-acids into tissue proteins. An increased rate of protein synthesis is thought to be a result of enhanced ability of ribosomes to translate messenger RNA. GH increases polyamine synthesis by increased ornithine decarboxylase activity; RNA synthesis by increasing RNA polymerase and DNA synthesis by increased DNA polymerase. Cell division is stimulated in several tissues (e.g. muscle and lymphoid tissue). In vivo GH lowers the respiratory quotient indicating an increased oxidation of fatty acids. The numbers of fat cells do not change but the fat cells are reduced in size. The stimulating effects of GH on skeletal tissue, and perhaps other tissues as well, is mediated by the formation of at least three peptides called somatomedins. GH is a protein with a molecular weight of about 22,000 and contains 191 amino-acid residues. The amino-acid sequence varies with the species. GH isolated from one species is not always effective in a different species. Use of GH isolated from pituitaries does not appear to be economically feasible. A chemical synthesis for human GH has been accomplished. However, biological activity equivalent to the native hormone has not been unequivocally established. Synthesis of bovine or porcine GH is feasible but will be expensive. A partial sequence of GH with 39 amino-acid residues has some biological activity. Synthesis of this shorter peptide would be considerably less expensive. Since proteins generally are not active orally, an economic procedure for prolonged parenteral administration would have to be devised. Althernative approaches would be the stimulation of endogeneous production of GH with hypothalmic GH releasing factor. This factor has not been identified but is probably a small peptide. Agents such as arginine, DOPA, and prostaglandins, which are known to stimulate GH release under some conditions, could also be considered. Another approach would be the implantation of sparganum from the spirometra family (a flatworm). This treatment is known to mimic GH effects in the rat. Implantation of a GH producing tumour could also be considered. Clearly these latter suggestions are quite speculative and would present some obvious problems...
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PMID:Role of growth hormone in improving animal production. 78 72

We have shown that a membrane fraction prepared from isolated human lymphoid nuclei contains endogenous DNA-synthesizing activity which is sensitive to RNAase. We have isolated a DNA polymerase from this fraction and partially purified it to what we estimate as about 10 000-fold. Its chromatographic behavior, template specificity, sedimentation constant, pH optimum, and sensitivity to N-ethylmaleimide suggest that the activity resembles but is not identical to DNA polymerase gamma (formerly called R-DNA polymerase). The membrane fraction also contains a minor activity which is due to polymerase beta, the low molecular weight (3.5 S) nuclear enzyme.
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PMID:Characterization of a DNA polymerase associated with an endogenous DNA-synthesizing complex isolated from human lymphoid cells. 84 46

The gene (pol) encoding the Epstein-Barr virus (EBV) DNA polymerase is a member of the "early" class of viral genes which are expressed shortly after activation of latent virus infection. First, mRNA from the EBV-producing cell line, B95-8, treated with 12-O-tetradecanoylphorbol-13-acetate and sodium butyrate to induce lytic replication and expression of this gene was analyzed. Northern (RNA) analysis revealed a message of 3.7 kb found only in induced cells. 5' mapping of pol mRNA by S1 nuclease and primer extension analyses indicates that transcription initiates at tightly clustered sites within a G + C-rich region 126 bp upstream of the open reading frame. The same initiation region was identified in two other EBV-infected cell lines, P3HR1 and Raji, after induction. Second, a 1.29-kb genomic fragment containing this region, when cloned upstream of the chloramphenicol acetyltransferase reporter gene, demonstrated promoter activity in lymphoid cells cotransfected with pEBV-RZ, a genomic expression construct that includes genes for the EBV immediate-early transactivator proteins, BZLF-1 and BRLF-1. Within the upstream 1.29-kb sequence, two regions of 140 bp and 101 bp appear to be needed for promoter activity. These results demonstrate that unlike most EBV genes studied thus far, the pol gene contains multiple transcriptional start sites. The upstream regulatory region of the promoter for the pol gene does not contain canonical promoter elements such as TATA and CAAT boxes and, furthermore, is not constitutively active but requires transactivation by two or more viral proteins.
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PMID:Regulation of the Epstein-Barr virus DNA polymerase gene. 131 4

Forty-nine children with recurrent acute lymphoblastic leukemia (ALL) were entered into a randomized Phase II trial evaluating 2'-deoxycoformycin (dCF) alone or in combination with adenine arabinoside (ara-A). 2'-Deoxycoformycin is an inhibitor of adenosine deaminase (ADA), an enzyme found in relatively high amounts in malignant lymphoid cells. Ara-A inhibits DNA polymerase and DNA synthesis. Because its efficacy in vivo as an anticancer agent is limited by its rapid inactivation by ADA, ara-A was combined with dCF to produce cytoreductive levels of ara-A. Twenty-four patients were assigned to receive dCF alone and 25 to receive the combination. No patient responded to dCF alone, and one patient developed a complete remission after treatment with the combination. The toxicity of dCF alone was minimal, except for one patient who became obtunded on day 5 following the first cycle of therapy. In contrast, five patients developed severe toxicity with the combination, including renal failure (three patients), hepatic failure (three patients), and neurologic toxicity (two patients). These results indicate that, at the doses and schedule used in this study, the combination of dCF and ara-A has significant toxicity and minimal activity against recurrent ALL in children.
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PMID:Lack of significant activity of 2'-deoxycoformycin alone or in combination with adenine arabinoside in relapsed childhood acute lymphoblastic leukemia. A randomized phase II trial from the Childrens Cancer Study Group. 144 10

The BCL-2 (B-cell lymphoma/leukemia-2) gene is frequently involved in t(14;18) translocations in non-Hodgkin's lymphomas and encodes a 26-kDa intracellular, membrane-associated protein. Expression of the BCL-2 gene has previously been correlated with cellular proliferation in normal and neoplastic lymphoid cells under a variety of experimental conditions. To examine the regulation of p26-BCL-2 protein levels during the cell cycle, we utilized the method of counterflow centrifugal elutriation to enrich for cells in various phases of the cell cycle. Relative levels of p26-BCL-2 protein were measured by immunoblotting, and comparisons were made with a cell cycle-regulated protein, p62-CYCLIN-A, and a protein whose levels are constant throughout the cell cycle, p36-PCNA (DNA polymerase-delta auxiliary factor). Relative levels of p26-BCL-2 and p36-PCNA did not vary among cell fractions enriched for specific phases of the cell cycle, whereas p62-CYCLIN-A was elevated in late S- and G2/M-phase cells. Similar results were obtained with lymphoma and leukemia cell lines that have either normal or translocated BCL-2 genes. These results obtained by elutriation were confirmed by pharmacologically inducing cell cycle arrest in proliferating lymphoid cell lines with hydroxyurea, quercetin, and nocodazole which blocked cells at S, G2, and M phases, respectively. Taken together, the data indicate that p26-BCL-2 is not a true cell cycle-regulated protein, although its levels can fluctuate in connection with changes in rates of cellular proliferation under some circumstances.
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PMID:Cell cycle analysis of p26-BCL-2 protein levels in proliferating lymphoma and leukemia cell lines. 158 93

DNA polymerase alpha is a DNA replicating enzyme expressed in all proliferating cells. This nuclear antigen in paraformaldehyde-postfixed frozen sections of normal, benign, and malignant tissues was identified by the peroxidase-antiperoxidase technique with the use of a mouse monoclonal antibody against bovine/human DNA polymerase alpha. The nuclei of normal proliferating cells were positive. Malignant tumors (n = 95) showed a higher proportion of positive nuclei than did low-grade malignant tumors (n = 7) or benign lesions (n = 67). The number of positive nuclei in squamous cell carcinomas (n = 19) was higher than in adenocarcinomas (n = 45). Eight (18%) adenocarcinomas and all five renal cell carcinomas had less than 10% positive cells, whereas in benign tissues, such as pituitary adenomas, a thymoma, reactive lymphoid lesions, and some benign mammary nodules, more than 10% of nuclei were labeled. In addition, foci of proliferating cells were clearly recognized. DNA polymerase alpha is, therefore, an excellent marker of proliferative activity that provides an approach to analyzing tumor cell heterogeneity not only in fully developed neoplasms, but also in their precursor lesions.
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PMID:DNA polymerase alpha. An immunohistochemical marker for proliferating cells in normal and neoplastic human tissues. 169 87

Within normal hemopoiesis, the intranuclear DNA polymerase TdT seems to be exclusively expressed by T and B lymphoid precursor cells. Double staining experiments showed that TdT can also be expressed in blast cells of certain acute myeloid leukemias. Recent reports described a very strong association between TdT expression and rearrangements of IgH and TcR genes in such AML specimens, suggesting a predominant lymphoid commitment of these TdT positive AML blasts. When submitting 24 serologically and morphologically well-characterized TdT positive AML specimens for additional genotypic analysis to determine the IgH and TcR gene configuration, we observed that only four had clonally rearranged IgH and/or TcR genes, whereas 20 had germ line configuration. This frequency is clearly lower than previously reported and not necessarily different from rearrangement frequencies reported for TdT negative AML (4-40%). It would seem to us, therefore, that the expression of TdT in otherwise well-defined AML blasts is not necessarily associated with a higher frequency of immunoglobulin and/or T cell receptor gene rearrangement.
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PMID:Terminal deoxynucleotidyl transferase and CD7 expression in acute myeloid leukemias are not associated with a high frequency of immunoglobulin and/or T cell receptor gene rearrangement. 169 41


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