Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0679427 (myeloblastosis)
 982 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A synthesis scheme for 3'-C-methyl-2'-deoxynucleosides and 3'-C-methylidene-2',3'-dideoxy-5-methyluridine has been proposed with 2-deoxyribose as the starting material. Methyl 5-O-benzoyl-2-deoxyribofuranose was oxidized and the mixture of the 3'-keto derivatives was separated into the alpha- and beta-anomers. The beta-keto derivative was converted by reaction with MeMgBr, and after reaction with thymine and subsequent deprotection 1-(3'-C-methyl-2'-alpha-deoxy-alpha-D-threo-pentofuranosyl)thymine and its beta-anomer were obtained. The same reactions with the alpha-keto sugar gave 1-(3'-C-methyl-2'-deoxy-alpha-D-erythro-pentofuranosyl)thymine and its beta-anomer. 1-(5-O-Benzoyl-3'-C-methyl-2'-deoxy-alpha-D-threo-pentofuranosyl)thymine was converted to a mixture of 3'-C-methylidene-2',3'-dideoxy-5-methyluridine and 3'-C-methyl-2',3'-dideoxy-2',3'-didehydro-5-methyluridine, which were separated. The stereoselectivity of the Grignard reagent's attachment to 2-deoxyfuranose 3-ulosides has been ruled by the substitute configuration at Cl. Also, the effect of the hydroxyl or OBz group configuration at C3 on the condensation stereoselectivity of 3-C-methyl-2-deoxyfuranosides with silylated thymine has been studied. The structure of the obtained compounds was proved by 1H NMR UV, 13C NMR, and CD spectroscopy, as well as elemental (C, H, N) analysis. The C2'-endo-C1'-exo conformation, the anti conformation of thymine in relation to the glycosidic bond, and the gauche+conformation in relation to the C4'-C5' bond are characteristic for the 3'-C-methyl-2'-deoxythymidine structure in the crystals. 3'-C-Methyl-2'-deoxythymidine 5'-triphosphate was synthesized and proved to be a competitive inhibitor, with respect to dTTP, of a number of DNA polymerases, including the reverse transcriptases of human immunodeficiency virus type 1 (HIV-1) and avian myeloblastosis virus (AMV). None of the DNA polymerases examined were able to incorporate this compound into the growing DNA chain. In contrast, 3'-C-methylidene-2',3'-dideoxy-5-methyluridine 5'-triphosphate was found to be incorporated at the 3'-end of the DNA chain by HIV-1 reverse transcriptase, albeit with very low efficiency. 3'-C-Methyl-2'-deoxy-5-methyluridine did not suppress HIV-1 replication in MT-4 cells at 500 microM while its 5'-phosphite derivative exhibited modest anti-HIV-1 activity.
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PMID:3'-C-branched 2'-deoxy-5-methyluridines: synthesis, enzyme inhibition, and antiviral properties. 128 82

The activity of the avian myeloblastosis virus (AMV) or the human immunodeficiency virus type 1 (HIV-1) protease on peptide substrates which represent cleavage sites found in the gag and gag-pol polyproteins of Rous sarcoma virus (RSV) and HIV-1 has been analyzed. Each protease efficiently processed cleavage site substrates found in their cognate polyprotein precursors. Additionally, in some instances heterologous activity was detected. The catalytic efficiency of the RSV protease on cognate substrates varied by as much as 30-fold. The least efficiently processed substrate, p2-p10, represents the cleavage site between the RSV p2 and p10 proteins. This peptide was inhibitory to the AMV as well as the HIV-1 and HIV-2 protease cleavage of other substrate peptides with Ki values in the 5-20 microM range. Molecular modeling of the RSV protease with the p2-p10 peptide docked in the substrate binding pocket and analysis of a series of single-amino acid-substituted p2-p10 peptide analogues suggested that this peptide is inhibitory because of the potential of a serine residue in the P1' position to interact with one of the catalytic aspartic acid residues. To open the binding pocket and allow rotational freedom for the serine in P1', there is a further requirement for either a glycine or a polar residue in P2' and/or a large amino acid residue in P3'. The amino acid residues in P1-P4 provide interactions for tight binding of the peptide in the substrate binding pocket.
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PMID:Mechanism of inhibition of the retroviral protease by a Rous sarcoma virus peptide substrate representing the cleavage site between the gag p2 and p10 proteins. 133 Oct 99

The structure of the retroviral proteinase from avian myeloblastosis associated virus (MAV) has been determined and refined at 2.2 A resolution. This structure is compared with those of homologous proteinases from Rous sarcoma virus (RSV) and human immunodeficiency type 1 virus (HIV). Through comparison with the structure of a proteinase-inhibitor complex from HIV, a model of a complex between MAV proteinase and a peptide substrate has been generated. Examination of this model suggests structural basis for the diverse specifications of viral proteinases.
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PMID:Structural studies of the retroviral proteinase from avian myeloblastosis associated virus. 133 25

Early events in the retroviral replication cycle include the conversion of viral genomic RNA into linear double-stranded DNA. This process is mediated by the reverse transcriptase (RT), a multifunctional enzyme that possesses RNA-dependent DNA polymerase, DNA-dependent DNA polymerase, and RNase H activities. In the course of studies of a recombinant RT of human immunodeficiency virus type 1 (HIV-1), we observed an additional, unexpected activity of the enzyme. The purified RT catalyzes a specific cleavage in HIV-1 RNA hybridized to tRNALys, the primer for HIV-1 reverse transcription. The cleavage at the primer binding site (PBS) of HIV RNA is dependent on the double-stranded structure of the HIV RNA-tRNALys complex. This RNase activity appears to be distinct from the RNase H activity of HIV-1 RT, as the substrate specificity and the products of the two activities are different. Moreover, Escherichia coli RNase H and avian myeloblastosis virus RT are unable to cleave the HIV RNA-tRNALys complex. We refer to this unusual activity as RNase D. Two lines of evidence indicate that the specific RNase D activity is an integral part of recombinant HIV RT. The specific RNase D activity comigrates with the other RT activities, DNA polymerase, and RNase H upon filtration on a Superose 6 gel column or chromatography on a phosphocellulose column. Moreover, three recombinant HIV-1 RT preparations expressed and purified in different laboratories by various procedures exhibit RNase D activity. Sequence analysis indicated that RNase D activity cleaves the substrate HIV-1 RNA-tRNALys at two distinct sites within the PBS sequence 5'-UGGCGCCCGA decreases ACAG decreases GGAC-3'. The sequence specificity of RNase D activity suggests that it might be involved in two stages during the reverse transcription process: displacement of the PBS to enable copying of tRNALys sequences into plus-strand DNA or to facilitate the second template switch, which was postulated to occur at the PBS sequence.
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PMID:Double-stranded RNA-dependent RNase activity associated with human immunodeficiency virus type 1 reverse transcriptase. 137 Oct 14

3'-Fluoro-2',3'-dideoxythymidine 5'-(alpha-methylphosphonyl)-beta,gamma- diphosphate and 2'-deoxythymidine-5'-(alpha-methylphosphonyl)-beta, gamma- diphosphate have been synthesized. Both compounds are incorporated into DNA chains during catalysis by reverse transcriptases of human immunodeficiency (HIV) and avian myeloblastosis (AMV) viruses, DNA polymerase beta from rat liver, terminal deoxynucleotidyl transferase from calf thymus and (at a very low rate) is by E. coli DNA polymerase I, Klenow fragment. The first compound is a termination substrate while the second is capable of multiple incorporation into the DNA chains. For instance, reverse transcriptase catalysis resulted in the appearance of 8 residues of second compound. DNA polymerases alpha and epsilon from human placenta incorporated none of the above compounds into DNA chains, although an inhibition of DNA synthesis by both compounds was observed with all enzymes mentioned. The 3'----5'-exonuclease activity of DNA polymerase I, Klenow fragment, hydrolyzed DNA fragments containing phosphonomethyl internucleoside groups, while such DNA fragments were resistant to the E. coli exonuclease III.
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PMID:Formation of phosphonester bonds catalyzed by DNA polymerase. 137 65

A comparison of the fidelity of reverse transcriptases (RT) from human immunodeficiency virus (HIV-1) and avian myeloblastosis virus (AMV) is made using RNA and DNA primer-template molecules in vitro. Selected template target sites containing either uracil or thymine are used to measure nucleotide insertion fidelities and to compare the efficiency of extending mismatched nucleotides at primer 3'-termini. HIV-1 reverse transcriptase is observed to incorporate as many as three consecutive mismatches and to continue efficient elongation from mismatched primer 3'-termini without discernible pausing. Nucleotide misinsertion and mispair extension efficiencies are similar for both enzymes on RNA and DNA templates having identical surrounding sequence. HIV-1 and AMV reverse transcriptases form G.T and G.U mismatches most efficiently, between 1.6 x 10(-4) and 7 x 10(-4), and both enzymes extend G.U with exceptionally high efficiencies, 2.7 x 10(-2) for HIV-1 RT and 4.5 x 10(-2) for AMV RT. Extension of the G.T mismatch is similar for AMV RT (5.8 x 10(-2) but 20-fold less efficient for HIV-1 RT. C.U and C.T mismatches are formed by both enzymes in a frequency range of 4.4 x 10(-5)-2.4 x 10(-4). HIV-1 RT extends these mismatches with slightly higher efficiencies (5.5 x 10(-3)-5.9 x 10(-3)) than AMV RT (5.6 x 10(-4)-2.1 x 10(-3)). Insertion of dTMP opposite U and T occur at about 1 x 10(-4)-2 x 10(-4) for HIV-1 RT. For AMV RT, formation of T.U mispairs occurs with an 8-fold lower efficiency, whereas insertion of dTMP opposite T is not detected. This particular DNA template sequence generates a pause site for AMV RT but not HIV-1 RT. HIV-1 RT dissociation rate constants are about 8-fold larger from a DNA primer bound to a DNA template (0.5 s-1), as compared with an RNA template (0.06 s-1) at one site, and are at most 2-fold larger at another site. The equilibrium binding constant for HIV-1 RT bound to DNA primed RNA and DNA templates appears to be similar, KD approximately 2.5 nM. Values of kpol from 0.3 to 1.5 nucleotides/s are obtained for HIV-1 RT at the RNA and DNA template sites used to measure insertion and extension fidelity. The relatively high efficiency of mispair extension catalyzed by reverse transcriptases with both RNA and DNA templates suggests that a significant component of retroviral genetic variability may be related to the ability of reverse transcriptases to continue efficient synthesis of DNA containing mismatches on both RNA and DNA templates.
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PMID:Comparison of HIV-1 and avian myeloblastosis virus reverse transcriptase fidelity on RNA and DNA templates. 137 33

The specificity of the proteinase of myeloblastosis-associated virus (MAV) was studied with (a) 21 substrate-based inhibitors, (b) 9 inhibitors with pseudopalindrome sequences, (c) 8 chimeric inhibitors, and (d) 3 compounds designed as human immunodeficiency virus 1 (HIV-1) proteinase inhibitors. The central inhibitory unit (transition state or cleaved bond analog) and the role of the inhibitor side chains from P4 to P4' were investigated. MAV proteinase prefers an aromatic side chain in P1 and a small aliphatic nonpolar chain in P2 and P2'. Residues in P5 and P4 positions are outside of the short catalytic cleft of the enzyme, but still influence binding considerably. The data obtained provide evidence that the MAV proteinase has generally lower specificity and poorer binding than the HIV proteinase.
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PMID:15gag proteinase of myeloblastosis-associated virus: specificity studies with substrate-based inhibitors. 141 1

In an attempt to understand the structural reasons for differences in specificity and activity of proteinases from two retroviruses encoded by human immunodeficiency virus (HIV) and myeloblastosis associated virus (MAV), we mutated five key residues predicted to form part of the enzyme subsites S1, S2 and S3 in the substrate binding cleft of the wild-type MAV proteinase wMAV PR. These were changed to the residues occupying a similar or identical position in the HIV-1 enzyme. The resultant mutated MAV proteinase (mMAV PR) exhibits increased enzymatic activity, altered substrate specificity, a substantially changed pH activity profile and a higher pH stability close to that observed in the HIV-1 PR. This dramatic alteration of MAV PR activity achieved by site-directed mutagenesis suggests that we have identified the amino acid residues contributing substantially to the differences between MAV and HIV-1 proteinases.
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PMID:An engineered retroviral proteinase from myeloblastosis associated virus acquires pH dependence and substrate specificity of the HIV-1 proteinase. 154 77

2',3'-Dideoxyuridine (ddUrd) exhibits poor if any anti-human immunodeficiency virus (HIV) activity in ATH8 and MT-4 cells. This is in agreement with the failure of ddUrd to be efficiently anabolized intracellularly to its 5'-triphosphate metabolite. However, 2',3'-dideoxyuridine-5'-triphosphate (ddUTP) proved to be a potent and selective inhibitor of the reverse transcriptase of HIV (Ki, 0.05 microM) and avian myeloblastosis virus (Ki, 1.0 microM). Bacterial DNA polymerase I, mammalian DNA polymerase alpha, terminal deoxyribonucleotidyl transferase, and Moloney murine leukemia virus reverse transcriptase were resistant to ddUTP. ddUTP is incorporated into the growing DNA chain principally at dTTP sites and inhibits further elongation. The potential of ddUTP as an anti-HIV therapeutic agent merits further investigation. However, to achieve this goal, it will be necessary to resort to techniques capable of delivering preformed phosphorylated ddUrd to the susceptible cells.
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PMID:Potent DNA chain termination activity and selective inhibition of human immunodeficiency virus reverse transcriptase by 2',3'-dideoxyuridine-5'-triphosphate. 168 52

A one-step procedure which uses enzymes in a crude extract of herpes simplex virus (HSV) type 1-infected cells to synthesize 5-[125I]iodo-2'-deoxyuridine triphosphate [( 125I]dUTP) from [125I]dU is described. The design of a one-step procedure for the purification of the product is also presented. The recovery of [125I]dUTP from [125I]dU varied between 50 and 75%, the radiochemical purity of the product was greater than 90%, and both synthesis and purification were completed within 8 h. The sensitivity and specificity of [125I]dUTP as a substrate for both DNA-dependent DNA polymerase (DNAp) and RNA-dependent DNA polymerase (reverse transcriptase, RT) were evaluated and compared to those of [3H]dTTP for the following specimens: purified cloned Klenow fragment, crude extracts of HeLa-, BHK-, and HSV-2-infected BHK cells, purified avian myeloblastosis virus RT, and purified cloned human immunodeficiency virus (HIV) RT. The [125I]dUTP was accepted as a substrate equally as well [3H]dTTP by all of the specimens at all of the concentrations tested. When the same amount of radiolabel was used, [125I]dUTP gave a sensitivity 10- to 25-fold higher than that of [3H]dTTP. The gain in sensitivity was due to the higher specific activity and a higher counting efficiency of the 125I-label compound. The use of [125I]dUTP also offered technical advantages over alternative substrates available, such as product separation without acid precipitation and exclusion of the need for scintillation cocktails. The half-life of the nucleic also gives a reasonable shelf-life for use in routine assays. Activity of less than 0.3 pg of HIV RT could be detected when the new substrate was used, and this made it possible to quantitate HIV RT antibodies (abs) in diluted serum samples without purifying the immunoglobulin. Analysis of 31 HIV-infected individuals showed that all of them had anti-HIV RT ab and that the amount of serum needed for 50% inhibition of the HIV RT activity corresponded to an amount of immunoglobulin 100-fold smaller (i.e., 0.02-31.4 micrograms) than has been previously reported. With the substrate it was also possible to detect DNAp activity in serum from healthy individuals, although a long-duration assay was required. In a long-duration assay the DNAp activity found in sera from healthy individuals was linear with respect to time, whereas the DNAp activity found in many sera from tumor patients was not. [125I]dUTP is judged to be an excellent substrate for detecting and quantifying the activity of various DNA-synthesizing enzymes and their blocking abs.
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PMID:Improved assays for DNA-polymerizing enzymes by the use of enzymatically synthesized 5-[125I]iodo-2'-deoxyuridine triphosphate, illustrated by direct quantitation of anti-HIV reverse transcriptase antibody and by serum DNA polymerase analyses. 169 11


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