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:3.1.30.2 (endonuclease)
18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Serological surveys have revealed that 30 to 50% of wild-caught African green monkeys have antibodies reactive to simian immunodeficiency virus (SIV), a retrovirus related to human immunodeficiency virus (HIV). Although the nucleotide sequence of one SIVagm isolate, Tyo1, was recently reported, the extent of genetic variability among SIVagm isolates remains to be determined. Restriction endonuclease mapping of infectious molecular clones of two SIVagm isolates (266 and 385), described in this note, revealed conservation of only 4 of 39 sites across the genome. Partial sequence analysis of the molecular clones revealed only 80% amino acid sequence conservation in the pol gene. Although the three Kenyan SIVagm isolates, Tyo1, 385, and 266, are more closely related to each other than to other primate lentiviruses, genetic variation among these three isolates is much greater than that observed previously among individual HIV type 1 (HIV-1), HIV-2, or SIVmac isolates. Less variability among HIV-1 and HIV-2 isolates could be explained by recent entry into the human population. The extensive genetic variation in these Kenyan SIVagm isolates should prompt continued examination of SIVagm variability from dispersed geographic regions; SIVagm strains much more closely related to HIV-1, HIV-2, or SIVmac which would be reasonable candidates for recent cross-species transmission may be found.
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PMID:Extensive genetic variability of simian immunodeficiency virus from African green monkeys. 246 10

A series of test substrates have been synthesized to establish the effect of termini on the putative exoribonuclease H activity of reverse transcriptase. Recombinant reverse transcriptase from human immunodeficiency virus, natural enzyme from avian myeloblastosis virus, and a known endonuclease, Escherichia coli ribonuclease H, cleaved relaxed, circular, covalently closed plasmids in which 770 consecutive residues of one strand were ribonucleotides. The avian enzyme also deadenylated capped globin mRNA with a covalently attached oligo(dT) tail at the 3' end. These results resolve a long-standing controversy--that the viral enzymes are obligatory exonucleases in vitro, based on their failure to cleave certain substrates for E. coli ribonuclease H, including circular poly(A).linear poly(T) and ribonucleotide-substituted supercoiled plasmids, but resemble endonucleases in vivo, based on their ability to degrade RNA in complex DNA.RNA hybrids. The data strongly suggest that the viral enzymes are endonucleases with exquisite sensitivity to the conformation of heteroduplexes. Inhibition of viral, but not cellular, ribonuclease H with ribonucleoside-vanadyl complexes further distinguishes these enzymes.
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PMID:Ribonuclease H activities associated with viral reverse transcriptases are endonucleases. 247 Nov 88

A gene encoding the human immunodeficiency virus-1 (HIV-1) TAT protein was chemically synthesized and expressed in HeLa cells and in a cell-free system. To facilitate both the assembly of the synthetic gene and further mutagenesis and gene fusion studies, several unique restriction endonuclease cleavage sites were included in the coding sequence without altering the encoded protein sequence. The synthetic TAT coding sequence was fused to a translation start signal and placed under SV40 early transcriptional control. Co-transfection of the TAT-encoding synthetic gene together with a reporter gene (chloramphenical acetyl transferase or beta-galactosidase) linked to an HIV LTR confirmed that the synthetic gene product exhibits similar activity to TAT expressed from HIV genomic DNA in the transactivation of the LTR. TAT mRNA prepared by cell-free transcription of the synthetic TAT coding sequence was also shown to produce functional TAT following microinjection into HeLa-derived cells containing an integrated reporter gene with the HIV LTR linked to beta-galactosidase.
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PMID:Chemical synthesis and expression of a gene encoding HIV-1 TAT protein. 254

Human immunodeficiency virus-1 (HIV-1) isolates obtained from chimpanzees that had undergone various immunosuppressive treatments were characterized by growth on various primary cells and cell lines as well as by restriction endonuclease analysis. Viruses recovered from animals inoculated with uncloned HIV showed genetic variation from the original inoculum, whereas viruses isolated from an animal infected with a molecular clone of HIV did not. In some cases, virus recovery was possible only after enrichment for CD4+ cells by panning, inoculation with a chimpanzee cytomegalovirus, or a combination of these procedures. These findings indicate a role for viral and host cofactors in the control of virus replication and suggest explanations for the absence of clinical manifestations in HIV-infected chimpanzees.
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PMID:Human immunodeficiency virus (HIV) from experimentally infected chimpanzees: isolation and characterization. 276 Sep 17

Information on the extent of genetic variability among non-human primate lentiviruses related to human immunodeficiency virus (HIV) is sorely lacking. Here we describe the isolation of two molecular clones from the simian immunodeficiency virus (SIV) and their use to derive restriction endonuclease maps of five SIV isolates from rhesus macaques and one from a cynomolgus macaque. Although similar, all six viral isolates are readily distinguishable; the single isolate from a cynomolgus macaque is the most different. The restriction endonuclease map of one macaque isolate (SIVMAC-251) is identical to that published by others for STLV-IIIAGM of African green monkeys and for HTLV-IV of humans. Nucleotide sequences from the envelope region of cloned SIVMAC-251 have more than 99% identify to previously published sequences for STLV-IIIAGM (refs 2, 4) and HTLV-IV (ref. 4). These results and other observations provide strong evidence that isolates previously referred to as STLV-IIIAGM and HTLV-IV by others are not authentic, but were derived from cell cultures infected with SIVMAC-251.
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PMID:Comparison of simian immunodeficiency virus isolates. 289 93

An anomalous sequence in certain lentiviruses was found to be related to a region in a completely different part of the simian retrovirus type I (SRV-I) and its close relative, the hamster intracisternal A particle (IAP-H18). The segment is not present in the human immunodeficiency virus (HIV), which is also a lentivirus, nor is it found in any one of a dozen other retroviruses whose sequences have been reported. These observations imply that a horizontal transfer of newly acquired genetic information has taken place between an SRV-I-type virus and one of the lentivirus type, and that this event occurred more recently than did the divergence of members of this latter group and HIV. Comparison of the viral nucleic acid sequences that encode these segments revealed the presence of imperfect direct nucleotide repeats resembling the retroviral endonuclease cleavage sites at the 5' and 3' ends of these regions.
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PMID:Relocation of a protease-like gene segment between two retroviruses. 310 74

A cytopathic human immunodeficiency virus type 1 (HIV-1) isolate containing multiple virus genotypes was molecularly cloned, and the biological activity of six randomly selected clones was assessed by transfection into human lymphoid or glial cell lines. Five infectious clones of HIV-1, termed N1T-A through -E, were isolated in this manner. Clones N1T-A, -B, -C, and -E could be distinguished by restriction endonuclease mapping whereas clones N1T-B and -D had identical maps with the enzymes used. Each clone exhibited a distinct host cell range as well as markedly different infection kinetics and cytopathogenic properties when tested in human cell lines of T-lymphocytic, monocytic, and astrocytic origin. In particular, infection with HIV-1 clone N1T-E was characterized by slow kinetics and lack of significant cytopathic effects in acutely and chronically infected cells. Clone N1T-A, similar to the parental isolate N1T, exhibited a wide host cell range, fast kinetics of infection, and high cytopathogenicity. These data indicate that HIV-infected individuals may carry multiple HIV-1 genotypes with distinct cytopathogenic potential and cell tropism. Analysis of virus isolates must take into account the contribution, or masking, of individual virus clones.
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PMID:Differences in cytopathogenicity and host cell range among infectious molecular clones of human immunodeficiency virus type 1 simultaneously isolated from an individual. 317 38

Simian immunodeficiency virus (SIV) was isolated from the total peripheral blood mononuclear cell population and the monocyte-macrophage adherent cell population of three seropositive green monkeys originating from Kenya. SIV from these African green monkeys (SIVagm) was isolated and continuously produced with the MOLT-4 clone 8 (M4C18) cell line but not with a variety of other cells including HUT-78, H9, CEM, MT-4, U937, and uncloned MOLT-4 cells. Once isolated, these SIVagm isolates were found to replicate efficiently in M4C18, SupT1, MT-4, U937, and Jurkat-T cells but much less efficiently if at all in HUT-78, H9, CEM, and MOLT-4 cells. The range of CD4+ cells fully permissive for replication of these SIVagm isolates thus differs markedly from that of previous SIV isolates from macaques (SIVmac). These SIVagm isolates had a morphogenesis and morphology like that of human immunodeficiency virus (HIV) and other SIV isolates. Antigens of SIVagm and SIVmac cross-reacted by comparative enzyme-linked immunosorbent assay only with reduced efficiency, and optimal results were obtained when homologous antibody and antigen were used. Western blotting (immunoblotting) of purified preparations of SIVagm isolate 385 (SIVagm385) revealed major viral proteins of 120, 27, and 16 kilodaltons (kDa). The presumed major core protein of 27 kDa cross-reacted antigenically with the corresponding proteins of SIVmac (28 kDa) and HIV-1 (24 kDa) by Western blotting. Hirt supernatant replicative-intermediate DNA prepared from cells freshly infected with SIVagm hybridized to SIVmac and HIV-2 DNA probes. Detection of cross-hybridizing DNA sequences, however, required very low stringency, and the restriction endonuclease fragmentation patterns of SIVagm were not similar to those of SIVmac and HIV-2. The nucleotide sequence of a portion of the pol gene of SIVagm385 revealed amino acid identities of 65% with SIVmac142, 64% with HIV-2ROD, and 56% with HIV-1BRU; SIVagm385 is thus related to but distinct from previously described primate lentiviruses SIVmac, HIV-1, and HIV-2. Precise information on the genetic makeup of these and other SIV isolates will possibly lead to better understanding of the history and evolution of these viruses and may provide insight into the origin of viruses that cause acquired immunodeficiency syndrome in humans.
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PMID:Simian immunodeficiency virus from African green monkeys. 317 40

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

HIVYU-6 and HIVYU-7 were isolated from an acquired immune deficiency syndrome patient (MK) and his asymptomatic sexual partner (MM), respectively. YU-6 readily infected not only peripheral lymphocytes from normal individuals but also human T-cell lines such as H9, HUT-78, MOLT-4 and MT-4; YU-7, on the other hand, could not infect H9 and MT-4 cells. Furthermore, although autologous serum failed to neutralize YU-6, it was neutralized by the heterologous serum from the partner. Restriction endonuclease analysis of YU-6 demonstrated that it was a mixture of viruses. We have isolated two clones from YU-6 (YU-6-a and YU-6-b) by a plaque assay method and showed that YU-6-a had one more KpnI site than YU-6-b. It was also evident that YU-7 derived from YU-6-a, but had already shifted genetically from YU-6-a. Transmission of human immunodeficiency virus through heterosexual contact and a possible genetic shift of YU-6-a, b and YU-7 from a common progenitor virus in vivo is discussed.
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PMID:Transmission and genetic shift of human immunodeficiency virus (HIV) in vivo. 350 21


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