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:3.1.27.1 (RNase)
16,360 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The interferon-(IFN)-inducible 2',5'-oligoadenylate (2-5A)/endoribonuclease L (RNase L) pathway plays a major role in the antiviral and antiproliferative effects of IFN. The 2-5A/RNase L pathway appears to be regulated by the cell-growth status or viral infection. Viruses, and picornaviruses in particular, have evolved strategies to escape the 2-5A/RNase L-pathway-associated antiviral activity. We have recently cloned a cDNA coding for RLI, a RNase-L-specific protein inhibitor. Its regulated expression by viral infection could provide a new strategy to modulate the 2-5A/RNase L pathway. Since RNase L had been shown to be down regulated upon encephalomyocarditis (EMCV) infection, we stably transfected HeLa cells with a RLI antisense cDNA expressing vector. Four independent clones named VAS1, VAS2, VAS3 and VAS4 and one clone transfected with the empty vector (VV) as control, were analyzed. The level of RLI was decreased by 20% for VAS1, 25% for VAS2, 75% for VAS3 and 50% for VAS4. The inactivation of RNase L observed during EMCV infection was decreased in these clones as compared to control HeLa cells. Here again the results vary between the four clones. The maximum inhibition of RNase L (90%) was observed in control cells and in VAS1 while 48% inhibition was observed in VAS4 and 25% in VAS3. The reversal in RNase L inhibition thus reflects closely the resulting RLI level, in keeping with a major role of RLI in EMCV-induced down regulation of 2-5A-binding activity of RNase L. Moreover, cells expressing a low level of RLI (VAS3 and VAS 4) are partially resistant to EMCV infection.
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PMID:RNase L inhibitor (RLI) antisense constructions block partially the down regulation of the 2-5A/RNase L pathway in encephalomyocarditis-virus-(EMCV)-infected cells. 966 Jan 77

RNase L (also termed 2-5A-dependent RNase) is a crucial enzyme involved in the molecular mechanism of interferon (IFN) action. Activated by 2',5'-oligoadenylate oligomers (2-5A), this enzyme controls the regulation of RNA stability in IFN-treated or virus-infected mammalian cells. Knowledge of RNase location within cells may provide additional information about its function. Previous work located RNase as a detergent-soluble molecule in nuclei and cytoplasm. In this study, we demonstrate that this enzyme was also present in a detergent-insoluble fraction associated with proteins of the cytoskeleton. A cellular fractionation procedure was used to prepare the cytoskeleton, which was shown to contain 2-5A binding activity not due to cytoplasmic contaminants. In contrast to the cytoplasmic fraction, which contained RNase L with a 2-5A-accessible site, the insoluble RNase molecular form of the cytoskeleton could not be assayed by the classic radiobinding method or the covalent UV cross-linking procedure, which only detects the 2-5A binding site in an open position, that is, free of 2-5A or with an unmasked 2-5A site. The 2-5A binding site present in the cytoskeleton was completely masked and not directly accessible to its 2-5A activator. This particular molecular form of RNase can be detected after a specific denaturing-renaturing treatment of the cytoskeleton, which separates the RNase from cytoskeletal proteins, unmasking the 2-5A site. The cytoskeletal RNase was no longer present at this site when cells were stimulated for a short time with 12-O-tetradecanoylphorbol-13-acetate (TPA). Our data suggest the existence of a pathway that targets the RNase to another subcellular location. To explore the issue further, we examined in vitro the ability of calcium and phospholipid-dependent protein kinase C (PKC) to catalyze significant phosphorylation of the RNase.
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PMID:Localization of a molecular form of interferon-regulated RNase L in the cytoskeleton. 966 Feb 42

2',5'-Oligoadenylate [2-5(A)] synthetases are a family of interferon-induced enzymes that polymerize ATP into 2'-5'-linked oligoadenylates in the presence of double-stranded RNA (dsRNA), their cofactor. The 2-5(A) molecules, in turn, activate the latent ribonuclease RNase L by promoting its dimerization. The 2-5(A) synthetase pathway has been implicated in interferon's antiviral and anticellular activities. In addition to their interesting cellular properties, these enzymes are also enzymologically interesting because they are the only known template and primer independent nucleotide (DNA or RNA)polymerases that synthesize 2'-5'-linked oligonucleotides. Moreover, their mode of activation by dsRNA remains unknown. In the past, biochemical and structure-function studies have been hampered by the lack of a convenient system for expressing recombinant 2-5(A) synthetases. These proteins are toxic to mammalian cells, probably because of RNase L activation, and proteins produced in bacteria do not have full enzymatic activity. To circumvent these problems, we have developed a baculovirus-insect cell system for high-yield expression of the small and medium isozymes. Here, methods are described for the production, purification, and characterization of the mouse small (9-2) (S. K. Ghosh, J. Kusari, S. K. Bandyopadhyay, H. Samanta, R. Kumar, and G. C. Sen, 1991, J. Biol. Chem. 266, 15293-15299) and human medium (P69) (I. Marie and A. G. Hovanessian, 1992, J. Biol. Chem. 267, 9933-9939) 2-5(A) synthetase isozymes and their mutants using the insect cell system. We also report methods for studying 2-5(A) synthetase-dsRNA interactions and protein-protein interactions among the subunits of the two isozymes.
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PMID:Production, purification, and characterization of recombinant 2', 5'-oligoadenylate synthetases. 973 8

RNA decay in IFN-treated cells is controlled by 2'5'-linked oligoadenylate (2-5A)-dependent RNase (RNase L), a uniquely regulated endoribonuclease that requires short 5'-phosphorylated, 2-5A for its activity. Because RNase L is also implicated in the regulation of cell proliferation, we monitored its expression in colorectal adenocarcinomas and noncancerous polyps from familial adenomatous polyposis patients. Elevated levels of RNase L mRNA and activity were found in 17 of 20 tumors compared with corresponding normal mucosa. An mAb against RNase L revealed elevated amounts of this RNase in sections of the tumors, largely in the base of the villi. The occurrence of elevated levels of RNase L seems to be an early event in colorectal tumorigenesis, suggesting that control of RNA turnover is an important step in tumor progression. These data also indicate that regulating RNase L activity may be a useful strategy in treating colorectal carcinomas.
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PMID:Elevated levels of 2',5'-linked oligoadenylate-dependent ribonuclease L occur as an early event in colorectal tumorigenesis. 981 40

RNase L is the 2',5'-oligoadenylate (2-5A)-dependent endoribonuclease that functions in interferon action and apoptosis. One of the intriguing, albeit unexplained, features of RNase L is its significant homology to protein kinases. Despite the homology, however, no protein kinase activity was detected during activation and RNA cleavage reactions with human RNase L. Similarly, the kinase plus ribonuclease domains of RNase L produced no detectable protein kinase activity in contrast to the phosphorylation obtained with homologous domains of the related kinase and endoribonuclease, yeast IRE1p. In addition, neither ATP nor pA(2'p5'A)3was hydrolyzed by RNase L. To further investigate the function of the kinase homology in RNase L, the conserved lysine at residue 392 in protein kinase-like domain II was replaced with an arginine residue. The resulting mutant, RNase LK392R, showed >100-fold decreases in 2-5A-dependent ribonuclease activity without reducing 2-5A- or RNA-binding activities. The greatly reduced activity of RNase LK392Rwas correlated to a defect in the ability of RNase L to dimerize. These results demonstrate a critical role for lysine 392 in the activation and dimerization of RNase L, thus suggesting that these two activities are intimately linked.
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PMID:Alternative function of a protein kinase homology domain in 2', 5'-oligoadenylate dependent RNase L. 986 63

The 2',5'-oligoadenylate-activated enzyme, RNase L, is an endoribonuclease implicated in the antiviral and apoptotic activities of interferons. To probe the genetics of the 2-5A system, the human and mouse genes were cloned, characterized, and compared. The first coding exon of both genes encodes the regulatory regions of RNase L, 67-70% of the proteins including nine ankyrin repeats, the 2-5A binding domain, and several protein kinase homology motifs. In contrast, the coding sequence for the ribonuclease domain in the mouse and human gene is divided among three exons. The transcriptional start site of the human RNase L gene was located in noncoding exon I by primer extension analysis. A complete coding sequence of mouse RNase L was obtained revealing a 735-amino acid protein with 64% identity to human RNase L. A hypothesis is presented concerning the evolutionary relationship of RNase L to both an ankyrin repeat protein kinase and the kinase-endoribonuclease. IRE1, that mediates the unfolded protein response.
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PMID:Analysis and origins of the human and mouse RNase L genes: mediators of interferon action. 1106 55

The human ISG20/HEM45 gene was identified independently on the basis of its increased level of expression in response to either interferon or estrogen hormone. Notably, the encoded protein is homologous with members of the 3' to 5' exonuclease superfamily that includes RNases T and D, and the proofreading domain of Escherichia coli DNA polymerase I. We provide here direct biochemical evidence that Isg20 acts as a 3' to 5' exonuclease in vitro. This protein displays a pH optimum of approximately 7.0, prefers Mn2+ as a metal cofactor, and degrades RNA at a rate that is approximately 35-fold higher than its rate for single-stranded DNA. Along with RNase L, Isg20 is the second known RNase regulated by interferon. Previous data showed that Isg20 is located in promyelocytic leukemia (PML) nuclear bodies, known sites of hormone-dependent RNA polymerase II transcription and oncogenic DNA viral transcription and replication. The combined data suggest a potential role for Isg20 in degrading viral RNAs as part of the interferon-regulated antiviral response and/or cellular mRNAs as a regulatory component of interferon and estrogen signaling.
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PMID:The human interferon- and estrogen-regulated ISG20/HEM45 gene product degrades single-stranded RNA and DNA in vitro. 1140 64

Gene expression of key enzymes in 2 antiviral pathways (ribonuclease latent [RNase L] and RNA-regulated protein kinase [PKR]) was compared in 22 patients with chronic fatigue syndrome (CFS), 10 patients with acute gastroenteritis, and 21 healthy volunteers. Pathway activation in the group of patients with infections differed significantly from that of the other 2 groups, in whom there was no evidence of upregulation. Therefore, assay of activation is unlikely to provide the basis for a diagnostic test for CFS.
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PMID:Antiviral pathway activation in patients with chronic fatigue syndrome and acute infection. 1198 43

The 2-5A/RNase L system is a regulated RNA decay pathway that mediates some of the antiviral and tumor suppressor activities of the interferons. Previously, we demonstrated that RNase L-null mice have increased susceptibility to viral infections and are partially deficient in induced and spontaneous apoptosis. To determine if RNase L functions in cellular, as well as innate, immunity, skin allograft rejection and contact hypersensitivity (CHS) experiments were performed in RNase L+/+ and RNase L-/- mice. Although no consistent alterations in CHS were found, we did observe a delay of 5 days in the acute rejection of class II major histocompatibility complex (MHC) disparate skin allografts in mice lacking RNase L. Accordingly, histologic examinations of the allografts harvested from RNase L-/- mice revealed a dramatic reduction in inflammatory infiltrates, suggesting a delay in T-cell priming or a deficiency in immune cell trafficking. Results consistent with a proinflammatory role for RNase L extend the known functions of the 2-5A/RNase L system beyond innate immunity into some, but not all, types of cellular immunity.
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PMID:Skin allograft rejection is suppressed in mice lacking the antiviral enzyme, 2',5'-oligoadenylate-dependent RNase L. 1195 48

2'-5' oligoadenylate (2-5 (A)) synthetases are major components of the antiviral pathways induced by interferons. In the presence of double-stranded RNA, they polymerize ATP to form 2-5 (A) oligomers that, in turn, activate the latent ribonuclease RNase L, causing mRNA degradation. These enzymes, unlike other nucleotidyl transferases, catalyze 2'-5', not 3'-5', phosphodiester bond formation between substrates bound to the acceptor and donor sites. Moreover, unlike other members of this extended family, the P69 isozyme of 2-5 (A) synthetase functions as a homodimer. Here, we report that the need for P69 dimerization is because of a crisscross enzyme reaction joining two substrate molecules bound to two opposite subunits. Consequently, although homodimers of mutants in the previously identified acceptor site, the donor site, or the catalytic site were inactive, selective heterodimers of the mutants were active because of subunit complementation. The catalytic site had to be present in the same subunit that contained the acceptor site, whereas the donor site had to be provided by the other subunit. These results allowed us to design a mutant protein that acted as a dominant-negative inhibitor of wt P69 but not of another isozyme of 2-5 (A) synthetase.
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PMID:Crisscross enzymatic reaction between the two molecules in the active dimeric P69 form of the 2'-5' oligodenylate synthetase. 1222 86


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