Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.13.1 (exoribonuclease)
 732 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The infectivity of replicative form RNA (RF-RNA) isolated from poliovirus-infected HeLa cells is completely resistant to the action of T-1 RNase but decreases after exposure to RNase A in the presence of 0.3 M NaCl. Under these conditions neither enzyme produces single-stranded nicks in RF-RNA. Three endonuclease-free exonuleases (RNase II, polynucleotide phosphorylase and spleen phosphodiesterase) rapidly destroy the infectivity of single-stranded RNA, but do not alter the infectivity of RF-RNA. It is concluded that RF-RNA does not contain single-stranded ends essential for infectivity. Indirect evidence suggests that all or most of the poly A region at the 3' end of the plus strand of infectious RF-RNA is base-paired to a poly U region at the 5 end of the minus strand.
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PMID:Poliovirus-induced infectious double-stranded RNA: Effect of RNA-degrading enzymes. 16 28

The exoribonuclease in bovine brain has been purified about 900-fold in 10% yield. The molecular weight is about 65,000. The enzyme is free from other ribonucleases of bovine brain. Studies of the mode of action of the enzyme show the following: (a) The enzyme cleaves both oligo- and polyribonucleotides exonucleolytically, initiating nucleolytic attack from the 5'-hydroxyl end to yield 3'-mononucleotides. The enzyme differs from spleen exonuclease in that it does not act on polydeoxyribonucleotides. (b) When the 5'-hydroxyl group is phosphorylated, the enzyme is inactive. (c) The enzymic action is processive in nature; the enzyme hydrolyzes one polynucleotide chain to completion before proceeding to the degradation of another chain.
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PMID:Purification and mode of action of exoribonuclease from bovine brain. 89 14

The effect of 3'-exoribonucleases on the polyadenylation of mRNA in Escherichia coli was studied by comparing the synthesis and levels of poly(A) RNA in wild-type E coli and mutant strains defective in the two major 3'-exoribonucleases: polynucleotide phosphorylase and ribonuclease II. Mutations which substantially reduced the activity of these 3'-exonucleases caused a 10-fold increase in pulse-labeling of total poly(A) RNA in intact cells. When the net rate of RNA synthesis was measured in permeabilized cells, the mutant with defective 3'-exonucleases showed 20- to 60-fold increased synthesis of total poly(A) RNA as well as of specific polyadenylated mRNAs, with less than two-fold changes in non-poly(A) RNA. Measurement of mRNA polyadenylation in permeable cells under conditions when 3'-exoribonucleases were inactive showed a 6-fold higher rate of poly(A) synthesis in the exonuclease-deficient mutant strain, suggesting a higher concentration of mRNA 3'-ends amenable to polyadenylation. Steady-state levels of poly(A) RNA, measured by the ability to serve as template for oligo(dT)-dependent complementary DNA synthesis, also increased more than 40-fold when the 3'-exonucleases were inactivated. Monitoring of the length of the poly(A) tracts by denaturing polyacrylamide gel electrophoresis showed chain lengths of up to 45 residues in the 3'-exonuclease-deficient mutant, whereas most of the poly(A) tracts in the parent strain were shorter than 12 residues. These results show that 3'-exonucleases reduce the level of polyadenylated mRNA in E coli not merely by causing its degradation but also by reducing its rate of synthesis, presumably by competing with poly(A) polymerase for the 3'-ends of mRNA.
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PMID:Polyadenylated mRNA in Escherichia coli: modulation of poly(A) RNA levels by polynucleotide phosphorylase and ribonuclease II. 924 86

Poly(A)-specific ribonuclease (PARN) is the only mammalian exoribonuclease characterized thus far with high specificity for degrading the mRNA poly(A) tail. PARN belongs to the RNase D family of nucleases, a family characterized by the presence of four conserved acidic amino acid residues. Here, we show by site-directed mutagenesis that these residues of human PARN, i.e. Asp(28), Glu(30), Asp(292), and Asp(382), are essential for catalysis but are not required for stabilization of the PARN x RNA substrate complex. We have used iron(II)-induced hydroxyl radical cleavage to map Fe(2+) binding sites in PARN. Two Fe(2+) binding sites were identified, and three of the conserved acidic amino acid residues were important for Fe(2+) binding at these sites. Furthermore, we show that the apparent dissociation constant ((app)K(d)) values for Fe(2+) binding at both sites were affected in PARN polypeptides in which the conserved acidic amino acid residues were substituted to alanine. This suggests that these residues coordinate divalent metal ions. We conclude that the four conserved acidic amino acids are essential residues of the PARN active site and that the active site of PARN functionally and structurally resembles the active site for 3'-exonuclease domain of Escherichia coli DNA polymerase I.
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PMID:Identification of the active site of poly(A)-specific ribonuclease by site-directed mutagenesis and Fe(2+)-mediated cleavage. 1174 7