Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.1.30.2 (endonuclease)
 18,621 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A computer analysis of the amino acid sequences from the putative gene products of retroviral pol genes has revealed a 150-residue segment that is homologous with the ribonuclease H of Escherichia coli. The segment occurs at the carboxyl terminus of the region assigned to the 90-kDa reverse transcriptase polypeptide. In contrast, a section nearer the amino terminus of this sequence can be aligned with nonretroviral polymerases. The order of activities in the pol gene is thus: polymerase-ribonuclease-endonuclease. On another note, all retroviral endonuclease sequences contain a consensus zinc-binding "finger." This should not be confused with the well-known zinc requirement of reverse transcriptases.
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PMID:Computer analysis of retroviral pol genes: assignment of enzymatic functions to specific sequences and homologies with nonviral enzymes. 242 13

The cytosolic untransformed molybdate-stabilized glucocorticoid-receptor complex from rat liver was eluted as a heterogenous peak containing two components with Stokes radii (Rs) of 8.3 nm and 7.1 nm when analyzed by size-exclusion HPLC even in the absence of molybdate. In contrast, the highly purified glucocorticoid receptor yielded a sharp symmetrical peak of Rs = 7.1 nm. We demonstrate that the 7.1-nm component could not result from a proteolytic degradation of the 8.3-nm receptor form. The same receptor heterogeneity was observed in thymus cytosol which contains less proteases than liver. After labeling with [3H]dexamethasone 21-mesylate and SDS/PAGE the same 94-kDa receptor band was revealed in both the 8.3-nm and 7.1-nm forms. Immunoblotting experiments showed that both the 94-kDa hormone-binding subunit and the 90-kDa heat-shock protein were present in the two different receptor forms. The 8.3-nm receptor form was converted to the 7.1-nm receptor form after treatment by ribonuclease A in the presence of molybdate and this effect was dose-dependent, being completely prevented by placental ribonuclease inhibitor (RNasin). In contrast, in the presence of molybdate, the 7.1-nm receptor form was ribonuclease-insensitive. Treatment of cytosol with RNase A in the absence of molybdate, partially shifted the untransformed receptor towards the 5.2-nm transformed receptor form. This effect was abolished by placental ribonuclease inhibitor. RNase S protein, an enzymatically inactive proteolytic fragment of RNase A, or S1 nuclease, which is specific for single-stranded nucleic acids, were ineffective when used instead of RNase A. In contrast, cobra venom endonuclease, which preferentially attacks double-stranded regions of small RNAs, caused a complete conversion of the 7-8-nm untransformed receptor to the 5.2-nm transformed receptor form. These results were not observed in the presence of molybdate. Addition of RNasin prior to heating cytosol in the absence of molybdate did not prevent the receptor from dissociating to the 5.2-nm form, suggesting that an endogenous RNase is not involved in the transformation process. The 7.1-nm receptor form was shifted to a 9.2-nm complex when incubated with an excess of GR 49 antireceptor antibody, whereas the 8.3-nm receptor form did not bind to the antibody.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:RNA binding to the untransformed glucocorticoid receptor. Sensitivity to substrate-specific ribonucleases and characterization of a ribonucleic acid associated with the purified receptor. 246 3

Sporamin, the major soluble protein of the sweet potato tuberous root, is coded for by a multigene family. Fourty-nine essentially full-length sporamin cDNAs isolated from tuberous root cDNA library have been classified by cross hybridization, restriction endonuclease cleavage pattern and ribonuclease cleavage mapping. All the cDNAs fall into one of the two distinct homology groups, subfamilies A and B, which correspond to the polypeptide classes sporamin A and B, respectively. At least 5 different sequences are detected in both of the 22 sporamin A and 27 sporamin B cDNAs. Comparison of the nucleotide sequences of the coding region of three each of sporamin A and B subfamily members, four from cDNAs and two from genomic clones, indicates that intra-subfamily homologies (94 to 98%) are much higher than inter-subfamily homologies (82 to 84%), and there are deletions or insertions of one or two codons at three locations which characterize each subfamily. Large portions of base substitutions in the coding region accompany amino acid substitutions. In contrast to the coding region, most of the structural differences among the members in the 5' and 3' noncoding regions are deletions or insertions.
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PMID:Structural relationship among the members of a multigene family coding for the sweet potato tuberous root storage protein. 249 73

A previously unreported endoribonuclease has been identified in Escherichia coli, which has a preference for hydrolysis of pyrimidine-adenosine (Pyd-Ado) bonds in RNA. It was purified about 7000-fold to give a single band after SDS/polyacrylamide gel electrophoresis; the eluted protein gave the same RNase specificity. The sizes of the native and denatured enzymes agreed suggesting that the enzyme exists as a monomer of approximately 26 kDa. It is called RNase M. The only other reported broadly specific endoribonuclease in E. coli is RNase I, a periplasmic enzyme. Based on differences in charge, heat stability and substrate specificity, it was clear that RNase M is not RNase I. The specificity of RNase M was remarkably similar to that of pancreatic RNase A even though the two enzymes differ in charge characteristics and size. Earlier studies had shown that mRNA from the lactose operon of E. coli is hydrolyzed in vivo primarily between Pyd-Ado bonds [Cannistraro et al. (1986) J. Mol. Biol. 192, 257-274] We propose that this major RNase activity accounts for these cleavages observed in vivo and that it is the endonuclease for mRNA degradation in E. coli.
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PMID:Purification and characterization of ribonuclease M and mRNA degradation in Escherichia coli. 265 29

An RNase activity was found to be present in rat brain and liver and was strongly bound to the nucleoprotein fractions of these tissues. It could not be solubilized by treatment with acid or by lipid solvents. The pattern of oligonucleotides produced during hydrolysis by this enzyme indicated that it was probably an endonuclease with restricted specificity. It was inhibited by zinc ions and by low pH.
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PMID:Occurrence of a nucleoprotein bound RNase in rat brain and liver. 308 63

The vast majority of nuclease activity in yeast mitochondria is due to a single polypeptide with an apparent molecular weight of 38,000. The enzyme is located in the mitochondrial inner membrane and requires non-ionic detergents for solubilization and activity. A combination of heparin-agarose and Cibacron blue-agarose chromatography was employed to purify the nuclease to approximately 90% homogeneity. The purified enzyme shows multiple activities: 1) RNase activity on single-stranded, but not double-stranded RNA, 2) endonuclease activity on single- and double-stranded DNA, and 3) a 5'-exonuclease activity on double-stranded DNA. Digestion products with DNA contain 5'-phosphorylated termini. Antibody raised against an analogous enzyme purified from Neurospora crassa (Chow, T. Y. K., and Fraser, M. (1983) J. Biol. Chem. 258, 12010-12018) inhibits and immunoprecipitates the yeast enzyme. This antibody inhibits 90-95% of all nuclease activity present in solubilized mitochondria, indicating that the purified nuclease accounts for the bulk of mitochondrial nucleolytic activity. Analysis of a mutant strain in which the gene for the nuclease has been disrupted supports this conclusion and shows that all detectable DNase activity and most nonspecific RNase activity in the mitochondria is due to this single enzyme.
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PMID:Purification and properties of the major nuclease from mitochondria of Saccharomyces cerevisiae. 328 39

An endonuclease specific for cruciform junctions has been purified from yeast cells treated with a DNA-damaging agent. The activity was followed through five chromatographic steps by assaying for the linearization of supercoiled plasmid DNA, which extrudes cruciform structures in vitro. The sites of cleavage on pColIR215 were sequenced, and nicks were located to positions symmetrically opposed across the cruciform junction. The products of cleavage were unit length linear duplexes that contained terminal hairpin loops. In contrast to pColIR215, the cleavage patterns of pXG540 plasmid DNA were found to be complex, and cuts were found up to 40 bases from an (A-T)34 sequence that extrudes into a cruciform. Little or no activity could be detected on single-stranded DNA, linear duplex DNA, or nicked circular duplex DNA. The nuclease was insensitive to RNase but was inactivated by treatment with proteinase K. Mg2+ was required as cofactor and could not be replaced by Mn2+, Ca2+, Co2+, or Cu2+. The native molecular weight of the activity was approximately 200,000 as estimated by gel filtration.
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PMID:Purification and properties of a nuclease from Saccharomyces cerevisiae that cleaves DNA at cruciform junctions. 330 13

La Crosse virus infection of BHK cells leads to a dramatic shutoff of not only host protein synthesis but also viral protein synthesis later in infection. This shutoff can be accounted for by the loss of the cytoplasmic cellular and viral mRNAs. The induction of mRNA instability requires extensive virus replication, since when cycloheximide is added early in infection the preexisting viral and cellular mRNAs do not decrease upon incubation of the cultures. Pretreatment of the cultures with actinomycin D does not affect the ability of La Crosse virus infection to induce mRNA instability, and examination of the rRNAs shows no evidence of specific degradation due to activation of the interferon-associated latent RNase. The induction of mRNA instability therefore does not appear to operate through an interferon pathway. Viral mRNA synthesis, on the other hand, is not turned off during infection, and the cap-dependent endonuclease involved in viral mRNA initiation may be responsible for the mRNA instability.
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PMID:La Crosse virus infection of mammalian cells induces mRNA instability. 333 45

The stabilities of different mRNA species were analyzed in a reticulocyte lysate system under protein-synthesizing conditions. In all cases examined the relative mRNA degradation by reticulocyte ribonucleases as well as by the interferon-modulated (2'-5') (A)n-dependent endonuclease correlated with the extent of (U)nA sequences within the 3' non-coding region. The experimental data presented indicate that according to their stabilities at least three major mRNA groups may be identified: (a) (U)nA-poor mRNAs (e.g. globin) are essentially stable and are only slightly degraded by the (2'-5')(A)n-dependent endonuclease; (b) mRNA species with intermediate (U)nA levels (e.g. Ig alpha and Ig mu heavy-chain mRNAs) are partially degraded by general ribonuclease activity and further degraded by the (2'-5')(A)n-dependent endonuclease and (c) (U)nA-rich mRNA species (such as c-myc and non-skeletal actin mRNAs) are inherently unstable and are extremely sensitive to degradation by general ribonuclease activity. A survey of mRNA nucleotide sequences demonstrated that without exception (U)nA-rich stretches appeared more frequently within the 3' non-coding region than in the coding or 5' non-coding regions. A comparison of 3' non-coding region sequences from 92 different mRNAs revealed that transiently expressed mRNAs, such as the interleukins, nerve growth factor, epidermal growth factor receptor, c-myc, c-fos, c-myb and several other oncogenes as well as interferons alpha, beta and gamma were exceptionally (U)nA-rich. It is postulated that differential mRNA stability may be partly determined by the primary nucleotide sequence and in particular by (U)nA sequences within the 3' non-coding region. This may represent a novel post-transcriptional strategy employed by the cell to selectively retain or destroy discrete mRNA species.
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PMID:Differential mRNA stability to reticulocyte ribonucleases correlates with 3' non-coding (U)nA sequences. 335

With the use of a reconstituted poly(ADP-ribosyl)ating enzyme system and three purified nucleases, micrococcal nuclease (MN), bull seminal RNase (BS RNase) and Ca2+, Mg2+-dependent endonuclease (BS DNase), as model acceptor proteins for ADP-ribose, the effect of ionic strength on the modification reaction was examined in detail. When these three nucleases were extensively poly(ADP-ribosyl)ated in this system at a low ionic strength (5 mM Tris), they were all inhibited by about 80% and the chain length of the polymer covalently bound to the nucleases was 13 to 23 ADP-ribose units. The observed inhibition was markedly prevented by increasing the ionic strength in the reaction mixture with a concomitant decrease in the polymer size bound to the nucleases. The NaCl concentrations required for decreasing the extent of the inhibition to half of the maximum were calculated to be 20, 50, and 100 mM for MN, BS RNase, and BS DNase, respectively. These values are similar to the NaCl concentrations required for decreasing the average chain lengths of the polymer to half, suggesting that the length of polymer is closely correlated to the extent of inhibition of these nucleases. DNA-binding affinities of these nucleases, expressed in terms of the NaCl concentrations required for eluting the enzymes from DNA-cellulose, were 140, 280, and 340 mM for MN, BS RNase, and BS DNase, respectively. Considering that maintainance of a ternary complex of poly(ADP-ribose) synthetase, acceptor and DNA may be essential for the modification reaction, the relatively strong salt effect observed in the modification of MN may be explained by its low DNA-binding affinity.
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PMID:Effect of ionic strength on chain elongation in ADP-ribosylation of various nucleases. 371 Oct 53


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