Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.49 (reverse transcriptase)
 31,746 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We sequenced two recombinant DNA clones constituting a single provirus of the milk-transmitted mouse mammary tumor virus characteristic of BR6 mice. The complete provirus is 9,901 base pairs long, flanked by 6 base-pair duplications of cellular DNA at the site of integration. Five extensive blocks of open reading frame corresponding to the gag gene, the presumed protease, the pol and env genes, and the open reading frame orf within the long terminal repeat of the provirus were readily discernible. Translation of gag, protease, and pol involved three different translational reading frames to produce the three overlapping polyprotein precursors Pr77, Pr110, and Pr160 found in virus-infected cells. Synthesis of the reverse transcriptase and endonuclease therefore required two separate frameshifts to suppress the termination codons at the ends of the Pr77 and Pr110 domains. Direct evidence is presented for translational readthrough of both stop codons in an in vitro protein synthesis system.
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PMID:Complete nucleotide sequence of a milk-transmitted mouse mammary tumor virus: two frameshift suppression events are required for translation of gag and pol. 302 77

Bovine leukemia provirus is reported to be integrated in the DNA of different infected mammalian cells. We observed morphological transformation in BLV infected sheep fetal spleen, kidney, thymus and sternal cultures. The presence of BLV specific sequences in their genome was established after digestion with the restriction endonuclease EcoRI and hybridization with a BLV specific probe. Human myeloma ARH77 and myeloid K562 cells infected with BLV were virus productive as detected by a reverse transcriptase assay. The presence of proviral sequences was confirmed after Southern blotting analysis. Restriction digestion by SacI enzyme yielded a complete 8.9 kb BLV provirus in infected ARH77 cells and a smaller 7.5 kb BLV fragment in infected K562 cells.
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PMID:Bovine leukemia provirus in the DNA of different infected host cells. 302 95

To study Moloney murine leukemia virus (M-MulV) proteins associated with the integration of proviral DNA into the host chromosome, we isolated endonuclease activities from purified virion preparations of the wild type and two of its replication mutants. A major endonuclease activity was identified in virions of M-MuLV; the enzyme catalyzed nicks in double-stranded DNA in the presence of either Mn2+ or Mg2+ and was stimulated by ATP. The endonuclease nicked DNA adjacent to all four nucleotides with some preference for G and C. The same enzyme, and in comparable amounts, was isolated from two virus replication mutants: dl2905, deficient in the processing of Pr65gag and Pr200gag-pol, and dl50401, deficient for the virus integration function. In the process of these experiments, the residual reverse transcriptase in mutant dl2905 was shown to be the mature size, implying that the uncleaved precursor lacks enzymatic activity. It appears that the major endonuclease activity found in virions of M-MuLV is not encoded by either the gag or pol genes.
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PMID:Characterization of endonuclease activities in Moloney murine leukemia virus and its replication-defective mutants. 303 6

A phylogenetic tree for different human immunodeficiency viruses type 1 (HIV1) and type 2 (HIV2), lentiviruses, and oncoviruses has been constructed by comparing the nucleotide sequences of the two regions of their pol genes that encode the reverse transcriptase and endonuclease/integrase. The analysis indicates that (1) different HIV1 strains form one cluster and their common ancestor diverged from the ancestor of HIV2, (2) the common ancestor of the HIV1 and HIV2 strains diverged from that of the lentivirus, and (3) the common ancestor of the lentivirus group and that of the oncoviruses diverged earlier than that. Divergence between the HIV1 and HIV2 strains seems to have occurred greater than 200 years ago, implying that AIDS has existed for a long time but went undetected. Furthermore, nonsynonymous changes are occurring uniformly through time, whereas synonymous changes are more variable among different lineages.
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PMID:Molecular evolution of the human immunodeficiency and related viruses. 338 28

The production of Moloney murine leukaemia virus from chronically infected cells was inhibited after starvation of glutamine. While the rate of synthesis of the precursor of the core proteins, Pr65gag, was not affected in the starved cells, its proteolytic processing was blocked. Pulse-chase experiments indicated that glutamine was required during the synthesis of Pr65gag to facilitate its subsequent processing. In addition, the synthesis of Pr200gag-pol, the precursor of the protease, reverse transcriptase and endonuclease, was inhibited in the glutamine-starved cells. Starvation for other essential amino acids such as tyrosine and isoleucine affected neither the synthesis nor the processing of the virus proteins. These results suggest that the readthrough mechanism which enables synthesis of the Pr200gag-pol polyprotein is modulated in the chronically infected cells by glutamine levels. Since the viral protease is part of the pol gene, its synthesis may be inhibited in the glutamine-starved cells and Pr65gag is therefore not processed.
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PMID:Glutamine starvation of murine leukaemia virus-infected cells inhibits the readthrough of the gag-pol genes and proteolytic processing of the gag polyprotein. 348 14

The retroviral reverse transcriptase is a multifunctional protein. Not only does it contain both RNA- and DNA-directed DNA synthesis activities but also it contains an endonuclease activity necessary for the integration of viral RNA and a RNase H. This latter activity can reduce to oligoribonucleotides viral RNA that has been reverse transcribed into minus-strand DNA. However, during avian retrovirus genome replication it does this in a highly specific manner so as to generate a specific 12-base primer for plus-strand DNA synthesis. Even though many other oligoribonucleotides are also made there is an efficient selection of the specific primer followed by its efficient utilization in plus-strand DNA synthesis, and subsequent removal. We have used a reconstructed system to gain an understanding of the factors that contribute towards these observed specificities.
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PMID:Retrovirus genome replication: priming specificities of plus-strand DNA synthesis. 350 85

We have purified from Moloney murine leukemia virus (Mo-MuLV) a protease that has the capacity of accurately cleaving the polyprotein precursor Pr65gag into the mature viral structural proteins. Both the NH2- and COOH-terminal amino acid sequences have been determined and aligned with the amino acid sequence deduced from the DNA sequence of Mo-MuLV by other workers. The results show that: (i) the protease is located at the 5' end of the pol gene, and the first four amino acids are overlapped with the 3' end of the gag gene; (ii) the fifth amino acid residue is glutamine, which is inserted by suppression of the UAG termination codon at the gag-pol junction; and (iii) the protease is composed of 125 amino acids with calculated Mr = 13,315, and the COOH terminus of the protease is adjacent to the NH2 terminus of reverse transcriptase. The map order of the gag-pol gene is proposed to be 5'-p15-p12-p30-p10-protease-reverse transcriptase-endonuclease-3'.
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PMID:Murine leukemia virus protease is encoded by the gag-pol gene and is synthesized through suppression of an amber termination codon. 388 15

Purified preparations of RNA-dependent DNA polymerase isolated from avain myeloblastosis virus contain RNase H activity. Labeled ribohomopolymers are degraded in the presence of their complementary deoxyribopolymer, except [(3)H]poly(U).poly(dA). The degradation products formed from [(3)H]poly(A).poly(dT) were identified as oligonucleotides containing 3'-hydroxyl and 5'-phosphate termini, while AMP was not detected. The nuclease has been characterized as a processive exonuclease that requires ends of poly(A) chains for activity. Exonucleolytic attack occurs in both 5' to 3' and 3' to 5' directions.RNase H has also been purified from E. coli. This nuclease degrades all homoribopolymers tested in the presence of their complementary deoxyribopolymers to yield oligonucleotides with 5'-phosphate and 3'-hydroxyl termini. E. coli RNase H has been characterized as an endonuclease.
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PMID:Mechanism of action of ribonuclease H isolated from avian myeloblastosis virus and Escherichia coli. 411 89

The primary structure analysis of the gag gene products of human T-cell leukemia virus (HTLV)-ICR has been nearly completed. A comparison of the amino acid sequences with the published nucleotide sequence of HTLV-IATK established that i) p19 which is known to share antigenic determinants with a protein present in normal thymic epithelium, is nevertheless virally coded. ii) The gene order and complete primary structure of the gag precursor (Pr55) which has been shown to be myristylated (My) at its N-terminus is My-p19-p24-p15-OH; and iii) the Pr55gag amino acid sequences of HTLV-ICR and HTLV-IATK are nearly identical showing only a single residue difference in the C-terminal region of p15. Antibodies to synthetic peptides inferred from the nucleotide sequence of the env gene of HTLV-IATK were also raised and used to identify and purify env precursor gPr62-68, surface glycoprotein gp46-51 and transmembrane protein p21. While most of the peptide sera were shown to be subgroup specific some of them detected antigenic determinants shared between protein homologs of viruses of subgroups I and II. Partial or complete amino acid sequences of both the gag and env gene coded proteins of bovine leukemia virus (BLV) structural proteins have also been determined. These extensive protein data together with nucleotide sequences confirm and extend our initial finding that HTLV and BLV are structurally and antigenically related and may have originated from common ancestor. The structural and immunological studies revealed also relationships between HTLV and a number of type C and type D retroviruses studied. One of the highly conserved sequences is shared by the transmembrane proteins of these retroviruses which have been implicated in immunosuppression. It is conceivable that these common regions have common biological function. Two previously unidentified proteins of BLV have also been purified and structurally characterized. Nucleotide sequences capable of coding for related products are present in HTLV. The nature and possible biological functions of these new BLV proteins and the putative HTLV gene products will be discussed. The size and complexity of the genome of the replication competent retroviruses are similar but not identical. The 35S RNA of all replication competent helper viruses is divided into three genes encoding the viral structural proteins: the gag (group-specific antigen) gene codes for the internal structural proteins, the pol (polymerase) gene codes for the enzymes protease, reverse transcriptase and endonuclease and the env (envelope) gene codes for the proteins of the viral envelope.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Structural and antigenic characterization of the proteins of human T-cell leukemia viruses and their relationships to the gene products of other retroviruses. 610 Jun 35

Free polysomes were isolated from the livers of rats maintained on a 60% casein diet to induce ornithine aminotransferase mRNA. Ornithine aminotransferase-synthesizing polysomes were immunoadsorbed using monospecific, affinity-purified antibody and Staphylococcus aureus cells. Poly(A+)RNA prepared from these polysomes by oligo(dT)-cellulose chromatography was used as a template for the synthesis of double-stranded cDNA by reverse transcriptase. Using the deoxyguanosine-5'-triphosphate-deoxycytidine-5'-triphosphate tailing method and pBR322 as a vector, recombinant molecules were produced and used to transform Escherichia coli. Two clones containing DNA complementary to ornithine aminotransferase mRNA were identified by colony hybridization and hybrid-arrest translation. A partial restriction endonuclease map of the ornithine aminotransferase cDNA inserts was constructed which spanned 1066 base pairs.
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PMID:Cloning of DNA complementary to ornithine aminotransferase mRNA. 612 4


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