Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The RNA-directed DNA polymerase of murine mammary tumor virus, a type B RNA tumor virus, was purified sequentially through DEAE-cellulose, phosphocellulose (step gradient), and phosphocellulose (linear salt gradient) chromatography followed by glycerol sedimentation centrifugation. During all stages of purification, coincident peaks of RNA-directed DNA polymerase activity, templated by polyribocytidylate-oligodeoxyguanidylate, and RNase H digestion of [3H]polyriboadenylate-polydeoxythymidylate were observed, and both enzymatic activities displayed a cation preference for magnesium. Under conditions that removed adventitiously associated nucleases, RNase H activity was found to co-purify with polymerase. The specificity of this nuclease was assayed with various prepared substrates, which indicated that the polymerase-associated RNase H activity was directed only against the RNA strand of an RNA-DNA hybrid. It is highly probable that RNase H (RNA-DNA hybrid: ribonucleotide-hydrolase, EC 3.1.4..34) and RNA-directed DNA polymerase of type B viruses are associated enzymatic activities analogous to those observed for avian and mammalian type C RNA tumor viruses.
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PMID:RNase H and RNA-directed DNA polymerase: associated enzymatic activities of murine mammary tumor virus. 6 21

We determined the complete nucleotide sequence of the intracisternal A-particle gene, IAP-H18, cloned from the normal Syrian hamster liver DNA. IAP-H18 was 7,951 base pairs in length with two identical long terminal repeats of 376 base pairs at both ends. On the coding strand, imperfect open reading frames corresponding to gag and pol of the retrovirus genome were observed, whereas many stop codons were present in the region corresponding to env. The putative H18 gag gene (809 amino acids) had a sequence homologous to the N-terminal half of the mouse mammary tumor virus gag gene and locally to the Rous sarcoma virus gag gene. The putative H18 pol gene (900 residues) was homologous to the Rous sarcoma virus pol gene almost throughout the entire region. Two conserved regions among the retrovirus pol genes have been reported. One presumably corresponds to the DNA polymerase and the RNase H domain, and the other corresponds to the DNA endonuclease domain of the multifunctional protein pol. By the comparison of the deduced amino acid sequences of the putative endonuclease domain of six representative oncovirus genomes, a phylogenetic tree of the oncovirus genomes was constructed, and the intracisternal A-particle (type A) genome was found to be more closely related to the mouse mammary tumor virus (type B) and squirrel monkey retrovirus (type D) genomes.
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PMID:Nucleotide sequence of the Syrian hamster intracisternal A-particle gene: close evolutionary relationship of type A particle gene to types B and D oncovirus genes. 299 63

We have examined the human mammary tumor cell line T47D and have found that these cells produce virus-like particles which band at the typical density for retroviral particles on a sucrose gradient, possess reverse transcriptase activity, and package HERV-K10-like sequences. Using this information and a bacterial expression system to identify long open reading frames, we have identified individual clones which have full-length open reading frames for reverse transcriptase and RNase H and which could encode the reverse transcriptase activity detected in these cells.
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PMID:Human endogenous retrovirus expression and reverse transcriptase activity in the T47D mammary carcinoma cell line. 864 2

It has been demonstrated that the half-life of c-myc mRNA is modulated in response to physiological agents. The elucidation of the decay process and the identification of the critical steps in the in vivo c-myc mRNA degradation pathway can be approached by following the fate of c-myc mRNA under the influence of such factors. IFN-alpha was the factor used to modulate c-myc mRNA half-life in HeLa 1C5 cells, a stable clone derived from HeLa cells. This cell line carries multiple copies of the c-myc gene, under the control of the dexamethasone inducible mouse mammary tumor virus-long terminal repeat (MMTV-LTR). Exposure of HeLa 1C5 cells to IFN-alpha resulted in a further 2-fold increase over the dexamethasone-induced c-myc mRNA. However, the c-myc mRNA in IFN-alpha treated cells was less stable than that in the control cells. RNase H mapping of the 3' untranslated region of c-myc mRNA revealed, in addition to the full length mRNA, three smaller fragments. These fragments were proven to be truncated, non-adenylated c-myc mRNA species generated in vivo. Exposure of HeLa 1C5 cells to Interferon-alpha before induction with dexamethasone resulted in the enhanced presence of these intermediates. RNase H analysis of c-myc mRNA after actinomycin D chase revealed that deadenylation led to the formation of a relatively more stable oligoadenylated c-myc mRNA population which did not appear to be precursor to the truncated intermediates. The detection of truncated 3' end c-myc mRNA adenylated fragments as well, implies that the c-myc mRNA degradation process may follow an alternative pathway possibly involving endonucleolytic cleavage.
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PMID:In vivo generation of 3' and 5' truncated species in the process of c-myc mRNA decay. 901 68