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:3.1.27.5 (RNase)
17,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

ATP : RNA adenyltransferase, purified from Escherichia coli, was used to add a series of adenosine residues to the 3'-end of MS2RNA. Incubations of the order of a few minutes at 37 degrees C were sufficient for synthesis of a short poly(A) chain that did not appreciably alter the hydrodynamic or electrophoretic properties of MS2 RNA. The size of the poly(A) tails was estimated by gel electrophoresis after prior hydrolysis of the primer RNA with pancreatic ribonuclease. These results were in good agreement with the values calculated on the basis of the relative amount of incorporated AMP. After the addition of a short poly(A) tail, approximately 50% of the treated material binds specifically to an oligo(dT)-cellulose column. The majority of the recovered poly(a)-containing RNA was still intact, as shown by analysis on polyacrylamide gel. After incubations beyond 6 min, slowly sedimenting material, also showing reduced electrophoretic mobility, was formed. Presumably this material corresponds to RNA chains to which long poly(A) tails are linked.
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PMID:The enzymic addition of poly(A) to the 3'-end of RNA using bacteriophage MS 2 RNA as a model system. 76 7

The synthesis of poly(A)-containing RNA by isolated mitochondria from Ehrlich ascites cells was studied. Isolated mitochondria incorporate [3H]AMP or [3H]UTP into an RNA species that adsorbs on oligo (dT)-cellulose columns or Millipore filters. Hydrolysis of the poly(A)-containing RNA with pancreatic and T1 ribonucleases released a poly(A) sequence that had an electrophoretic mobility slightly faster than 4SE. In comparison, ascites-cell cytosolic poly(A)-containing RNA had a poly(A) tail that had an electrophoretic mobility of about 7SE. Sensitivity of the incorporation of [3H]AMP into poly(A)-containing RNA to ethidium bromide and to atractyloside and lack of sensitivity to immobilized ribonuclease added to the mitochondria after incubation indicated that the site of incorporation was mitochondrial. The poly(A)-containing RNA sedimented with a peak of about 18S, with much material of higher s value. After denaturation at 70 degrees C for 5 min the poly(A)-containing RNA separated into two components of 12S and 16S on a 5-20% (w/v) sucrose density gradient at 4 degrees C, or at 4 degrees and 25 degrees C in the presence of formaldehyde. Poly(A)-containing RNA synthesized in the presence of ethidium bromide sedimented at 5-10S in a 15-33% (w/v) sucrose density gradient at 24 degrees C. The poly(A) tail of this RNA was smaller than that synthesized in the absence of ethidium bromide. The size of the poly(A)-containing RNA (approx. 1300 nucleotides) is about the length necessary for that of mRNA species for the products of mitochondrial protein synthesis observed by ourselves and others.
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PMID:The synthesis of polyadenylic acid-containing ribonucleic acid by isolated mitochondria from Ehrlich ascites cells. 98 39

Purified rat liver mitochondria were shown to synthesize poly(adenylic acid) (poly(A)) in vitro. Detection of the poly(A) synthesizing activity was facilitated by addition of NaF to the reaction was shown to be poly(A) by its insensitivity to digestion with pancreatic RNase and RNase T1, its degradation by venom phosphodiesterase and its retention on poly (uridylic acid) 20-23 AMP units and it was covalently attached to the endogenous RNA in the mitochondria. Poly(A) synthesis required ATP and a divalent ion and was maximally active in the pH range of 7-8. The reaction was inhibited by atractyloside, cordycepin triphosphate, Rose Bengal, rifamycin derivative AF/103, sodium pyrophosphate, and N-ethylmaleimide. These studies indicate that the mitochondrial poly(A) polymerase previously described in our laboratory (Jacob, S.T., Rose, K.M., and Morris, H.P. (1974), Biochim. Biophys. Acta 361, 312-320) is involved in the posttranscriptional addition of poly(A) sequence to mitochondrial RNA.
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PMID:Poly(adenylic acid) synthesis in isolated rat liver mitochondria. 99 Feb 63

Evidence is presented from three experimental systems to support the allosteric model of Walker et al. (1975) (Biochem. J. 147, 425-433) which explains the substrate-concentration-dependent transition observed in the RNAase (ribonuclease)-catalysed hydrolysis of 2':3'-cyclic CMP (cytidine 2':3'-cyclic monophosphate). 1. Kinetic studies of the initial rate of hydrolysis of 2':3'-cyclic CMP show that the midpoint of the transition shifts to lower concentrations of 2':3'-cyclic CMP in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, 3'-UMP and Pi; 2'-CMP and 2'-UMP do not cause such a shift. 2. Trypsin-digestion studies show that a conformational change in RNAase to a form less susceptible to tryptic inactivation is induced in the presence of the substrate analogues 3'-CMP, 5'-CMP, 3'-AMP, and 3'-UMP. 2'-CMP, 2'-AMP and 2'-UMP do not induce this conformational change. 3. Equilibrium-dialysis experiments demonstrate the multiple binding of molecules of 3'-CMP, 3'-AMP and 5'-AMP to a molecule of RNAase. 2'-CMP binds the ratio 1:1 over the analogue concentration range studied.
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PMID:Further evidence for an allosteric model for ribonuclease. 127 91

Erythropoietin (EPO) is mainly produced in the kidneys and is regulated by blood oxygen availability. Studies with isolated perfused kidneys have established that an oxygen-sensing system exists intrarenally but the mechanisms involved are poorly understood. Using a quantitative RNase protection assay, we have demonstrated oxygen-dependent EPO mRNA production in isolated perfused rat kidneys, with EPO mRNA levels increasing 30-fold when perfusate pO2 was reduced from 474 to 25 mm Hg. To determine if the high amplitude changes in EPO mRNA levels in response to hypoxia are mediated by cyclic AMP, four agents, which activate the cyclic AMP system in different ways, were administered to isolated kidneys perfused over a range of perfusate pO2. Salbutamol and N6-ethyl carboxamidoadenosine, which activate adenylate cyclase, dibutyryl cyclic AMP (a cyclic AMP analogue) and forskolin did not augment EPO mRNA production, and no significant differences in the regression of log (EPO mRNA) on perfusate pO2, were found between experimental groups exposed to each of these compounds and controls. We conclude that the rapid increase in EPO mRNA levels in response to hypoxia is not mediated or substantially modulated by a cyclic AMP-dependent mechanism.
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PMID:Rapid oxygen-dependent changes in erythropoietin mRNA in perfused rat kidneys: evidence against mediation by cAMP. 132 27

alpha 1-Adrenergic receptors (ARs) are members of the guanine nucleotide-binding protein-coupled receptor superfamily. The genes for all ARs described thus far are intronless. We report here the cloning and the nucleotide sequence of the gene for the human alpha 1B-AR. It consists of two exons and a single large intron of at least 20 kilobases which interrupts the coding region at the end of the putative sixth transmembrane domain. The deduced amino acid sequence of the encoded receptor has a high degree of homology to the cloned hamster, rat, and dog alpha 1B-ARs. To characterize the encoded protein, a fusion gene constructed by splicing together exon 1 and exon 2 was expressed transiently in COS-1 cells. The transfected gene fusion product resulted in the production of an alpha 1B-AR with ligand binding characteristics indistinguishable from those of the expressed hamster alpha 1B cDNA. Evidence that the human alpha 1B-AR gene we have isolated is indeed transcribed is the finding of similar sized (2.8-kilobase) transcripts in human heart and other tissues by Northern blot analysis when either exon 1 or exon 2 is used as a probe. Moreover, using primers designed to span the exon 1/exon 2 boundary, a polymerase chain reaction product generated from single-stranded DNA prepared from human heart mRNA had the exact size and nucleotide sequence predicted for a transcript in which exon 1 is spliced to exon 2. The 5'-flanking region (924 base pairs (bp)) of exon 1 contains neither a TATA box nor a CAAT box but is high in GC content (70%) and contains several Sp1 binding sites (GC boxes), consistent with promoters described for housekeeping genes. The 5'-untranslated region also contains a putative cyclic AMP response element. Primer extension studies and RNase protection assays suggested that there are several potential transcription start sites in most tissues with a predominant site located 173 bp upstream from the translation start site. The 3'-flanking region contains a putative polyadenylation signal (ATTAAA) 492 bp downstream from the stop codon. The genomic organization of the human alpha 1B-AR with a single large intron interrupting its coding region differs from those of other ARs as well as muscarinic and 5-hydroxy-tryptamine receptors, which are intronless. The location of the intron in the human alpha 1B-AR gene is also unique among those members of the G-protein-coupled receptor family that do possess introns.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Genomic organization and expression of the human alpha 1B-adrenergic receptor. 132 50

On the basis of molecular dynamics and free-energy perturbation approaches, the Glu46Gln (E46Q) mutation in the guanine-specific ribonuclease T1 (RNase T1) was predicted to render the enzyme specific for adenine. The E46Q mutant was genetically engineered and characterized biochemically and crystallographically by investigating the structures of its two complexes with 2'AMP and 2'GMP. The ribonuclease E46Q mutant is nearly inactive towards dinucleoside phosphate substrates but shows 17% residual activity towards RNA. It binds 2'AMP and 2'GMP equally well with dissociation constants of 49 microM and 37 microM, in contrast to the wild-type enzyme, which strongly discriminates between these two nucleotides, yielding dissociation constants of 36 microM and 0.6 microM. These data suggest that the E46Q mutant binds the nucleotides not to the specific recognition site but to the subsite at His92. This was confirmed by the crystal structures, which also showed that the Gln46 amide is hydrogen bonded to the Phe100 N and O atoms, and tightly anchored in this position. This interaction may either have locked the guanine recognition site so that 2'AMP and 2'GMP are unable to insert, or the contribution to guanine recognition of Glu46 is so important that the E46Q mutant is unable to function in recognition of either guanine and adenine.
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PMID:RNase T1 mutant Glu46Gln binds the inhibitors 2'GMP and 2'AMP at the 3' subsite. 135 Jun 42

In order to study the structure-function relationship of an RNase T2 family enzyme, RNase Rh, from Rhizopus niveus, we investigated the roles of three histidine residues by means of site-specific mutagenesis. One of the three histidine residues of RNase RNAP Rh produced in Saccharomyces cerevisiae by recombinant DNA technology was substituted to a phenylalanine or alanine residue. A Phe or Ala mutant enzyme at His46 or His109 showed less than 0.03%, but a mutant enzyme at His104 showed 0.54% of the enzymatic activity of the wild-type enzyme with RNA as a substrate. Similar results were obtained, when ApU was used as a substrate. The binding constant of a Phe mutant enzyme at His46 or His109 towards 2'-AMP decreased twofold, but that at His104 decreased more markedly. Therefore, we assumed that these three histidine residues are components of the active site of RNase Rh, that His104 contributes to some extent to the binding and less to the catalysis, and that the other two histidine residues and one carboxyl group not yet identified are probably involved in the catalysis. We assigned the C-2 proton resonances of His46, His104, and His109 by comparison of the 1H-NMR spectra of the three mutant enzymes containing Phe in place of His with that of the native enzyme, and also determined the individual pKa values for His46 and His104 to be 6.70 and 5.94. His109 was not titrated in a regular way, but the apparent pKa value was estimated to be around 6.3. The fact that addition of 2'-AMP caused a greater effect on the chemical shift of His104 in the 1NMR spectra as compared with those of the other histidine residues, may support the idea described above on the role of His104.
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PMID:Evidence that three histidine residues of a base non-specific and adenylic acid preferential ribonuclease from Rhizopus niveus are involved in the catalytic function. 142 2

The modes of binding of adenosine 2'-monophosphate (2'-AMP) to the enzyme ribonuclease (RNase) T1 were determined by computer modelling studies. The phosphate moiety of 2'-AMP binds at the primary phosphate binding site. However, adenine can occupy two distinct sites--(1) The primary base binding site where the guanine of 2'-GMP binds and (2) The subsite close to the N1 subsite for the base on the 3'-side of guanine in a guanyl dinucleotide. The minimum energy conformers corresponding to the two modes of binding of 2'-AMP to RNase T1 were found to be of nearly the same energy implying that in solution 2'-AMP binds to the enzyme in both modes. The conformation of the inhibitor and the predicted hydrogen bonding scheme for the RNase T1-2'-AMP complex in the second binding mode (S) agrees well with the reported x-ray crystallographic study. The existence of the first mode of binding explains the experimental observations that RNase T1 catalyses the hydrolysis of phosphodiester bonds adjacent to adenosine at high enzyme concentrations. A comparison of the interactions of 2'-AMP and 2'-GMP with RNase T1 reveals that Glu58 and Asn98 at the phosphate binding site and Glu46 at the base binding site preferentially stabilise the enzyme-2'-GMP complex.
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PMID:Modes of binding of 2'-AMP to RNase T1. A computer modeling study. 152 9

The int-2 gene, which encodes a member of the fibroblast growth factor family, is expressed at specific sites and times during mouse development. In certain embryonal carcinoma cell lines, multiple int-2 transcripts accumulate when the cells are induced to differentiate with retinoic acid and dibutyryl cyclic AMP. Nuclear run-on analyses indicate that the apparent induction of int-2 expression results from an increase in the rate of transcription initiation. Six distinct types of RNA have been delineated, originating from three promoters and terminating at either of two polyadenylation sites. Since each transcript appears to encode the same protein, this complexity may reflect the need for lineage-specific or differentiation-dependent control of expression. By comparing the kinetics of induction and turnover of the different RNA species, we show that the choice of promoter or length of the 3'-untranslated region has no significant effect on the half-lives of the various mRNAs. To further evaluate control at the transcriptional level, we have shown that a 1.7-kilobase fragment of int-2 genomic DNA, when fused to the chloramphenicol acetyltransferase gene, can act as a regulated promoter(s) in differentiated versus undifferentiated embryonal carcinoma cells. This segment of DNA encompasses the three promoter regions previously delineated by RNase mapping plus about 900 base pairs of additional upstream sequences.
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PMID:Transcriptional regulation of the int-2 gene in embryonal carcinoma cells. 164 13


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