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

Interferon-treated HeLa cells were incubated with [3H]uridine to label mRNA and were then exposed to the double-stranded RNA poly(inosinic acid).poly(cytidylic acid) (In.Cn). The incubation with In.Cn greatly enhanced the decay of mRNA. When the cells were incubated in this way in the presence of cycloheximide, which blocks ribosome movement along mRNA, extensive polysome degradation was detected in interferon-treated cells. Products of degradation of mRNA were recovered from monosomes which were presumably formed as a result of endonucleolytic breaks of mRNA. This endonucleolytic activity was correlated with the formation of 2',5'-oligo(A) by an enzyme induced by interferon and activated by double-stranded RNA; the 2',5'-oligo(A) was previously shown to activate an endonuclease in cell extracts. The 2',5'-oligo(A) levels in cells were measured by a competition-binding assay. Details of the procedure used are described, including synthesis of highly radioactive (2'-5')pppA3[32P]cytidine 3',5'-diphosphate, separation of 2',5'-oligo(A) binding from degrading activities, and specificity of the assay.
...
PMID:Double-stranded RNA causes synthesis of 2',5'-oligo(A) and degradation of messenger RNA in interferon-treated cells. 616 69

DNA from a human adult was fragmented by partial digestion with restriction endonuclease EcoRI and cloned in lambda Charon 4A. Clone C15, with a human DNA insert of 17 X 10(3) bases, was identified as containing a gene for the fibroblast interferon, interferon beta 1. Restriction mapping shows that this gene, located on a 1840-base EcoRI fragment, is not interrupted by introns. Moreover, we show that this human genomic DNA fragment is able to direct the synthesis of active human interferon beta 1 in Escherichia coli. Interferon activity of up to 7 X 10(6) U/l was recovered from phage lysates by chromatography on Cibacron blue--Sepharose, and had the same immunological properties and species specificity as interferon produced by human fibroblasts.
...
PMID:Synthesis of human interferon beta 1 in Escherichia coli infected by a lambda phage recombinant containing a human genomic fragment. 617 27

One of the mediators of interferon action is an endonuclease system. This consists of (2'-5')(A)n synthetase, which, if activated by double-stranded RNA, converts ATP into (2'-5')(A)n and RNase L, a latent endoribonuclease, which binds (2'-5')(A)n and is thereby activated. We report here that a derivative of (2'-5')(A)n (i.e. (2'-5')pppApApA[32P]pCp) can be covalently cross-linked by UV irradiation to a protein in cytoplasmic extracts from mouse Ehrlich ascites tumor cells. This protein has an apparent molecular weight of 77,000 as determined by gel electrophoresis in sodium dodecyl sulfate. It appears to be identical with RNase L according to the following criteria: co-chromatography on DEAE-cellulose and Sephacryl S300. The gel filtration in Sephacryl S300 reveals that the apparent molecular weight of the protein is between 70,000 and 90,000, indicating that it is a monomer. The cross-linking is oligonucleotide specific. It is inhibited by 10 nM (2'-5')pppApApA or 1 microM (2'-5')ApApA, i.e, compounds known to block, even at low concentration, the binding of (2'-5')pppApApApCp to RNase L. (3'-5')ApApA inhibits only at a 0.1-1 mM concentration, and 1 mM ATP, 2'-AMP, or 5', 3'-pCp have no effect. (2'-5')pppApApApCp was also cross-linked to a protein with a molecular weight of about 78,000 (as determined by gel electrophoresis in sodium dodecyl sulfate) in cytoplasmic extracts from human (HeLa) cells and to protein(s) with molecular weight(s) of 75,000-77,000 (as determined by gel electrophoresis in sodium dodecyl sulfate) in nuclear extracts from Ehrlich ascites tumor cells.
...
PMID:Interferon action. Covalent linkage of (2'-5')pppApApA(32P)pCp to (2'-5')(A)n-dependent ribonucleases in cell extracts by ultraviolet irradiation. 617 33

Treatment with interferon protected HeLa cells from infection with reovirus. This virus apparently activated an antiviral mechanism that was detected by the presence of (2'-5')oligoadenylate [(2'-5')An] in intact cells. The (2'-5')An was previously shown to activate an endoribonuclease, RNase L. We measured (2'-5')An by a sensitive competition-binding assay in cells infected at different multiplicities and for different lengths of time. Nanomolar concentrations of (2'-5')An were detected in cells infected at a multiplicity of greater than 5 after 2 h of infection, the time at which the infecting virions were uncoated. The level of (2'-5')An increased up to 6 h postinfection but declined afterward. To establish whether viral mRNAs were cleaved by RNase L, we analyzed the RNA extracted from infected cells by a highly specific hybridization assay on Northern blots. Full-sized reovirus mRNAs were detected in control infected cells, but not in interferon-treated infected cells, at 6 h postinfection. At this time, a nuclease activity could be detected in these cells by demonstration of cleavage of rRNA, degradation of cellular mRNA, and polysome breakdown in the presence of emetine. Since this inhibitor freezes ribosomes, cleavage of mRNA between ribosomes could only be accounted for by an endonuclease, presumably RNase L.
...
PMID:Synthesis of (2'-5')oligoadenylate and activation of an endoribonuclease in interferon-treated HeLa cells infected with reovirus. 617 44

Heterogeneous nuclear RNA contains double-stranded regions that are not found in mRNA and that may serve as recognition elements for processing enzymes. The double-stranded regions of heterogeneous nuclear RNA prepared from HeLa cells promoted the synthesis of (2',5')oligoadenylate [(2',5')oligo(A) or (2'5')An] when incubated with (2',5')An polymerase. This enzyme is present in elevated levels in interferon-treated cells, and labeled heterogeneous nuclear RNA incubated with extracts of these cells is preferentially cleaved, since mRNA included in the same incubations is not appreciably degraded. The cleavage of heterogenous nuclear RNA is caused by the synthesis of (2'5')An and by a "localized" activation of the (2',5')An-dependent endonuclease, since it was enhanced by ATP, the substrate of the (2',5')An polymerase, and inhibited by 2'-dATP and ethidium bromide. Both of these compounds suppress the synthesis of (2',5')An, the first by competitive inhibition and the latter by intercalating into double-stranded RNA. The possible role of double-stranded regions and of the (2',5')An polymerase-endonuclease system in the processing of heterogeneous nuclear RNA is discussed.
...
PMID:Heterogeneous nuclear RNA promotes synthesis of (2',5')oligoadenylate and is cleaved by the (2',5')oligoadenylate-activated endoribonuclease. 618 Mar

Eleven chimeric plasmids have been constructed which direct the synthesis of mature human fibroblast (IFN-beta 1) or leukocyte interferon (IFN-alpha A) proteins under the control of the E. coli trp promoter. The plasmids differ with respect to the nucleotide spacing between the Shine-Dalgarno sequence of the trp leader and the ATG translation start signal of the interferon genes. By utilizing a unique Xba I endonuclease site located within the spacer region of the expression plasmids, the spacings were altered from 2-10 nucleotides or 7-15 nucleotides for the fibroblast and leukocyte interferon expression plasmids, respectively. The optimal spacing for expression, as determined by interferon assay, is 9 nucleotides for both types of transcripts, despite differences in nucleotide sequence within the spacer region and downstream from the AUG initiator. Yields of IFN-alpha A varied about six-fold, while among the different IFN-beta 1 expression plasmids a range of more than 100-fold in interferon production was observed. The difference in the range of variation between the IFN-alpha A and IFN-beta 1 plasmids is attributed partly to changes in messenger RNA secondary structure within the ribosome binding sites which affect message half-life.
...
PMID:Increased synthesis in E. coli of fibroblast and leukocyte interferons through alterations in ribosome binding sites. 618 21

Infectious leukemia virus production by two chronically infected NIH/MOL lines was strongly inhibited by interferon treatment of the cells. The corresponding degree of inhibition in JLSV-11 cells was much lower. Multiplication of encephalomyocarditis virus in all three cell lines was barely affected by interferon treatment. Replication of vesicular stomatitis virus, on the other hand, was highly sensitive to interferon in the JLSV-11 line and in one NIH/MOL line but was practically insensitive in the other NIH/MOL line. Anticellular actions of interferon were more pronounced in the JLSV-11 line than in the others. In response to interferon treatment, 2',5'-oligoadenylate synthetase activity was induced to a high level in JLSV-11 cells and to lower levels in the NIH/MOL lines. We failed to detect any 2',5'-oligoadenylate-dependent endonuclease activity in extracts of these cells. Double-stranded RNA-dependent protein kinase activity was present in extracts of interferon-treated NIH/MOL cells, but it was barely detectable in extracts of interferon-treated JLSV-11 cells. The above studies demonstrated that interferon could differentially affect the replication of three different viruses in three different cell lines, including two seemingly identical NIH/MOL lines, and that certain tentative conclusions can be drawn regarding the roles of different interferon-inducible enzyme markers in the different antiviral actions of interferons.
...
PMID:Differential antiviral effects of interferon in three murine cell lines. 618 40

A mouse fibroblast cell-line deficient in thymidine kinase (Ltk(-) aprt(-)) fails to show an anti-viral response when treated with interferon. After introduction of a viral tk gene into these cells the resultant clones showed normal responses to interferon. However, one such tk-containing clone (C6) spontaneously lost its ability to respond to interferon by inducing an antiviral state although it retained its ability to induce the enzyme oligo(2'-5' A)-synthetase. This sub-clone (6A) still expressed thymidine kinase activity but restriction endonuclease analysis indicated an alteration in the sequences flanking the exogenous viral tk gene. Our results suggest that a modification in the exogenous viral DNA sequences led to a loss of interferon sensitivity.
...
PMID:Thymidine kinase genes and the induction of anti-viral responses by interferon. 619 Jun 77

RD-114 is a human sarcoma-derived cell line which is chronically infected with the RD-114 retrovirus. In a previous study, we found that treatment of these cells with human interferon-alpha or human interferon-gamma causes a marked inhibition of RD-114 virus production, but that the replication of exogenous vesicular stomatitis or encephalomyocarditis virus is not impaired. In the present study, we report that neither type of interferon has strong inhibitory effects on DNA synthesis or on multiplication of the cells. We also failed to detect a double-stranded RNA-dependent protein kinase activity in extracts of both interferon-treated and untreated cells. However, a low level of 2',5'-oligoadenylate [2,5(A)] synthetase activity was detectable in extracts of interferon-treated cells. 2,5(A)-dependent endonuclease L activity was detectable in extracts of both untreated and interferon-treated cells. This was probably responsible for the inhibition of protein synthesis observed upon introduction of 2,5(A) to RD-114 cells. In many cells, interferon has been found to induce synthesis of several proteins demonstrable by autoradiographic analysis of slab gels on which extracts of interferon-treated and radiolabelled cells are separated. Using a similar method, no such induced protein synthesis was detectable in interferon-treated RD-114 cells. Our results indicate that RD-114 cells are resistant to most known actions of interferons except for the antiretroviral action to which they are as sensitive as any other cell line.
...
PMID:Antiviral, anticellular and enzyme-inducing activities of interferons in RD-114 cells. 619 49

In interferon-treated mouse L cells, following infection with a DNA-containing virus, vaccinia, synthesis of unique 2'-5'-linked oligonucleotides of the general formula ppp5'A2'(p5'A)n, abbreviated as 2-5A, was detected by competition radiobinding assay. In addition, degradation of rRNA into discrete and characteristic products, similar to those produced by 2-5A-activated endonuclease, was observed. The degradation of rRNA may represent a significant component of antiviral action of interferon in vaccinia virus-infected cells.
...
PMID:Degradation of rRNA in interferon-treated vaccinia virus-infected cells. 619 24


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---