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

---

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

Rubromycins, a class of quinone antibacterials, were discovered to selectively inhibit human immunodeficiency virus-1 (HIV-1) RNA-directed DNA polymerase (reverse transcriptase) (RT) activity more potently than cellular DNA polymerase alpha. beta- and gamma-rubromycin each inhibited equipotently HIV-1 RT and avian myeloblastosis virus RT, in a concentration-dependent manner, and were significantly weaker as inhibitors of calf thymus DNA polymerase alpha. These agents inhibited HIV-1 RT reversibly, were competitive with respect to template.primer, and were noncompetitive with respect to TTP. Dixon analyses yielded HIV RT Ki values of 0.27 +/- 0.014 and 0.13 +/- 0.012 microM for beta- and gamma-rubromycin, respectively. Similarly, using DNA polymerase alpha, the Ki values were 25.1 +/- 4.3 and 3.9 +/- 0.6 microM for beta- and gamma-rubromycin, respectively. Because these agents were toxic to noninfected human T lymphoid cells using concentrations at or above 6 microM, HIV-1 infectivity studies were carried out at 0.8-6 microM. At these concentrations, which are below the range expected to provide protection, no significant antiviral activity was observed. Although beta- and gamma-rubromycins did not possess sufficient HIV RT inhibitory potency or selectivity versus mammalian DNA polymerase to demonstrate antiviral activities, these studies support the hypothesis that specific molecules containing quinone functional groups can selectively inhibit viral polymerase activities over cellular polymerase activities. In addition, these studies suggest that rubromycins may be lead structures for the development of more potent and selective agents.
...
PMID:Inhibition of human immunodeficiency virus-1 reverse transcriptase activity by rubromycins: competitive interaction at the template.primer site. 169 17

Lymphotropic herpesviruses such as Epstein-Barr virus and Herpesvirus saimiri are commonly grouped as gamma-herpesviruses, although overall genome organization and numerous biological properties are quite different in the viruses. To define the relationship more precisely, we sequenced the Kpnl fragments F (6.5 kb) and C (9.8 kb) of the H.saimiri strain No. 11 genome; these DNA fragments were found to contain the genes coding for equivalents of the major DNA binding protein, a putative glycoprotein transport polypeptide, the glycoprotein B, and the DNA polymerase of herpes simplex virus. This DNA segment represents the longest block of contiguous genes with pronounced sequence homologies between herpesviruses of known DNA primary structure. Comparisons confirmed that the two gamma-herpesviruses are related; the group is, however, even more diverse than the alpha-herpesviruses represented by their prototypes, herpes simplex virus and varicella-zoster virus. H. saimiri DNA is strongly depleted in the dinucleotide CpG, possibly the consequence of de novo methylation of persisting viral DNA in lymphoid cells.
...
PMID:Structural organization of the conserved gene block of Herpesvirus saimiri coding for DNA polymerase, glycoprotein B, and major DNA binding protein. 215 88

The Epstein-Barr virus early antigen diffuse component (EA-D) is essential for Epstein-Barr virus DNA polymerase activity, and its activity is suppressed during latent infection. We investigated the regulation of the promoter (BMRF1) for this early gene by studying its responsiveness in vitro to two immediate-early viral transactivators, BZLF1 (Z) and BRLF1 (R), focusing on the differences in response in lymphoid cells and epithelial cells. In lymphoid cells, Z or R alone produced only small increases in EA-D promoter activity, whereas both transactivators together produced a large stimulatory effect. In epithelial cells, the Z transactivator alone produced maximal stimulation of the EA-D promoter; the effect of R and Z together was no greater than that of Z alone. Deletional analysis and site-directed mutagenesis of the EA-D promoter demonstrated that in epithelial cells the potential AP-1 binding site plays an essential role in Z responsiveness, although sequences further upstream are also important. In lymphoid cells, only the upstream sequences are required for transactivation by the Z/R combination, and the AP-1 site is dispensable. These data suggest that EA-D (BMRF1) promoter regulation by Z and R is cell type specific and appears to involve different mechanisms in each cell type.
...
PMID:The Epstein-Barr virus (EBV) BMRF1 promoter for early antigen (EA-D) is regulated by the EBV transactivators, BRLF1 and BZLF1, in a cell-specific manner. 216 95

Polymerase chain reaction (PCR) is a novel tool for the in vitro amplification of DNA segments up to several kb. Repeated cycles of DNA synthesis by heat-stable Taq DNA polymerase enables to obtain more than 10(5) copies of the target sequence. Recently its enormous attitude of amplification has been applied for the detection of tumor-specific gene alterations. Examples include the detection of point mutation of RAS oncogenes at codons 12, 13, and 61 and the detection of minimal residual neoplastic cells in patients in complete clinical remission. Among many kinds of tumor specific gene translocations, BCR-ABL gene in t(9;22)(q34;q11) and BCL-2-IgH gene in t(14:18)(q32;q21) have been successfully PCR-amplified around their fused regions. In lymphoid malignancies gene rearrangements of T cell receptor chain or immunoglobulin heavy chain can be used as clonal markers for leukemic cells. PCR technique permits the detection of leukemia DNA at dilution of 10(-4) to 10(-6). Although further investigation of patients' follow-up in large scale is needed, this technique seems to hold promise for the monitoring of residual neoplastic cells.
...
PMID:[Polymerase chain reaction (PCR)--a novel tool for the molecular diagnosis of neoplasms]. 220 61

To detect the proliferating cells in situ, a monoclonal antibody against human DNA polymerase alpha (pol alpha) was employed because this enzyme is known to be present in the nucleus of the cells in G1, S, and G2 phases. In addition, the surface phenotype of pol alpha-positive proliferating lymphocytes in diseased lymph nodes was determined by double staining consisting of immunoperoxidase and immunoalkaline phosphatase methods with various monoclonal antibodies against lymphocyte membrane antigens. In the paracortical area of lymph nodes with reactive changes, proliferating cells were 17% or less, and most of them were helper T-cells, although suppressor T-cells and B-cells also proliferate to a certain extent. In contrast, the proliferating cell population in malignant lymphomas was generally more than 40%, and it showed a single surface phenotype, indicating monoclonal proliferation. In addition, an unusual T-cell antigen phenotype of proliferating cells was observed in some cases of peripheral T-cell lymphomas. Thus, this double staining provided the authors with valuable information regarding the proportion, localization, and surface phenotype of proliferating cells, which should be useful for diagnosis of the diseases of lymphoid system.
...
PMID:Double immunoenzymatic detection of surface phenotype of proliferating lymphocytes in situ with monoclonal antibodies against DNA polymerase alpha and lymphocyte membrane antigens. 243 27

The short-term incubation of rat thymocytes with 12-O-tetradecanoylphorbol-13-acetate (TPA) resulted in a significant increase in sialyltransferase (S-T) activity and a decrease in terminal deoxyribonucleotidyl transferase (TdT) activity. The ratio of peanut agglutinin (PNA)-positive cells and of TdT-positive cells in TPA-treated cells also decreased. However, TPA had no significant effects on the viability, morphology, DNA synthesis, and DNA polymerase alpha activity of the cells. More marked changes were observed by incubating a non-T, non-B human lymphoid leukaemia cell line with TPA. Similar findings were also noted in TPA-treated mouse thymocytes. These changes may represent an aspect of TPA-induced differentiation of murine thymocytes.
...
PMID:Effects of 12-O-tetradecanoyl phorbol-13-acetate (TPA) on rat thymocytes. 278 10

The 2',3'-dideoxynucleosides (ddNs) are currently undergoing clinical evaluation as antiretroviral agents in HIV-infected individuals. When phosphorylated, the ddNs (ddNTPs) function as chain-terminating substrate analogues with reverse transcriptase, thereby inhibiting HIV replication. These nucleoside analogues can also inhibit, by chain-terminating additions, the primitive lymphoid DNA polymerase, terminal deoxynucleotidyl transferase (TdT). To determine the effect of possible intracellular chain-terminating additions of ddNMPs by TdT, we exposed a series of TdT-positive and TdT-negative cell lines to 2',3'-dideoxyadenosine (ddA), a representative ddN. At ddA concentrations 25-fold higher than required for inhibition of HIV replication, progressive dose-related cytotoxicity was observed in the TdT-positive cell lines. This was accentuated by the adenosine deaminase inhibitor Coformycin (CF), presumably by enhancing the intracellular generation of ddATP from ddA. A central role of TdT in mediating the ddA/CF cytotoxicity was suggested by studies in a pre-B-cell line rendered TdT positive by infection with a TdT cDNA-containing retroviral vector. After a 48-hour continuous exposure period to 250 mumol/L ddA and 30 mumol/L CF, 30% cell death was observed in the TdT-negative parental line, whereas 90% cell death was observed in the TdT-positive daughter line. Exposure of fresh TdT-positive leukemic cells to ddA/CF for 72 hours ex vivo resulted in cytotoxicity (six cases of acute lymphocytic leukemia [ALL]) while not affecting TdT-negative acute leukemic cells (six cases). We conclude that ddA/CF selectively damages TdT-positive cells, presumably by chain-terminating additions of ddAMP, and that this may have therapeutic relevance in TdT-positive malignant disease.
...
PMID:2',3'-Dideoxyadenosine is selectively toxic for TdT-positive cells. 283 1

Terminal deoxynucleotidyl transferase (Tdt), a unique DNA polymerase found only in lymphoid cells, may be involved in the generation of immunoglobulin-combining site diversity. To study the actual metabolic function of the enzyme, we developed a system in which Tdt expression is induced under defined culture conditions. We found that pharmacologic agents that raise intracellular cyclic AMP levels, such as caffeine, induce a three- to 10-fold increase in enzyme biosynthesis rate and activity. This phenomenon is observed only in pre-B cell lines of human or murine origin.
...
PMID:Cyclic AMP induces terminal deoxynucleotidyl transferase in immature B cell leukemia lines. 298 68

Peripheral blood lymphocytes (PBLs) isolated from woodchucks chronically infected with the woodchuck hepatitis virus (WHV) carry low levels of nonreplicating WHV DNA. When PBLs from chronic carrier woodchucks were activated in culture with the generalized mitogen lipopolysaccharide (LPS), WHV DNA replication was initiated in cells obtained from one of three animals examined. Intracellular WHV core particles, containing WHV DNA replication intermediates, RNA/DNA hybrid molecules, and an active endogenous DNA polymerase, appeared 3 days after the start of LPS stimulation. After 5 to 7 days of LPS stimulation, WHV DNA-containing particles, which displayed the properties of intact, mature virions, were released into the culture medium. These studies provide evidence for reactivation of a latent WHV infection of circulating lymphoid cells and indicate that the presence of nonreplicating hepadnaviral DNA in lymphoid cells represents a potentially active infection following cellular activation.
...
PMID:Mitogen-induced replication of woodchuck hepatitis virus in cultured peripheral blood lymphocytes. 326 87

Until recently, lineage fidelity was thought to be preserved in leukaemic cells, which by available tests showed surface markers and enzymatic patterns characteristic of an appropriate normal cell lineage and stage of differentiation. Our data indicate that this theory is too restrictive. If leukaemogenesis occurs in pluripotent progenitors in a relatively high percentage of cases, we would propose a model in which lymphoid and myeloid differentiation antigens are expressed simultaneously until the progenitor cell commits to a single lineage. Lineage commitment could involve external factors, e.g. growth factors (Sherr et al, 1985), that cause genes specific for the opposite lineage to be 'switched off'. The control of gene expression in mammalian cells and the specific chromosomal sites of genes coding for the various lineage-associated markers remain uncertain. However, recent studies indicate that most, if not all, leukaemic cells contain chromosomal abnormalities, many involving rearrangements of DNA (Williams et al, 1986). Since the control of eukaryotic gene expression is known to involve numerous sequence elements, some acting at a distance from the site of transcription (Dynan and Tjian, 1985), genetic perturbations within the cell (e.g. a reciprocal translocation) could be expected to deregulate certain genes, leading to their under- or overexpression analogous to activation of the c-myc oncogene by the 8;14 translocation in Burkitt's lymphoma. Thus, an almost infinite variety of cell lineage-related phenotypes could be expected from this mechanism alone, even if the transforming event did not involve a pluripotent stem cell. Also, we have hypothesized that enzymes such as TdT, a DNA polymerase that catalyses polymerization of deoxyribonucleotides without a DNA template, could serve as a modifier of DNA sequences, permitting otherwise inactive genes to be expressed (Stass and Mirro, 1985). It is interesting that most cases of childhood acute mixed-lineage leukaemia are TdT positive, even though this is not true for the chronic leukaemias of adults. It is now clear that unusual combinations of myeloid and lymphoid cell lineages are much more common in acute leukaemia than have been generally recognized or suspected. The traditional division of the acute leukaemias into ALL and AML may not be the most accurate way to represent this class of haematological malignancies. That mixed-lineage leukaemia may require alternative therapy is a clinically important observation and underscores the need for comprehensive testing of blast cells at diagnosis.(ABSTRACT TRUNCATED AT 400 WORDS)
...
PMID:Lineage heterogeneity in acute leukaemia: acute mixed-lineage leukaemia and lineage switch. 353 42


<< Previous 1 2 3 4 5 6 7 Next >>

---