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)

Proteolytic activity in a protein fraction of a rat thymocyte nuclear matrix was found to increase 1-2 h after gamma-irradiation or administration of dexamethazone. Cycloheximide did not prevent the observed protease activation. Neither histons nor thymocyte nuclear matrix proteins were subjected to proteolysis after exposure to radiation or the hormone. Such proteolysis inhibitors as phenylmethylsulfonyl fluorine, trasilol, and partly leupeptine inhibited nuclear DNA degradation in irradiated and dexamethazone treated thymus lymphocytes. In all appearance, this effect was not due to Ca/Mg-dependent endonuclease inactivation. The same was observed in the system of autolytic chromatin degradation in isolated thymocyte nuclei.
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PMID:[Chromatin degradation in the death of thymic lymphocytes induced by radiation or dexamethasone: the necessity for a stage of preliminary proteolysis]. 203 99

A one- and two-dimensional NMR study has been performed on seven A(2'-5')A(2'-5')A fragments containing 9-(3'-fluoro-3'-deoxy-beta-D-xylofuranosyl)-adenine (AF) or 3'-fluoro-3'-deoxyadenosine (AF) residues at different positions, and on the corresponding monomers. A(2'-5')A(2'-5')A served as a reference compound. The fluoro substituent governs the conformation of the sugar ring: an AF residue displays mainly N-type sugar and the ring is considerably flattened (phi N approximately 30 degrees) compared to AF residues (phi S approximately 40 degrees), which exhibit almost pure S-type conformation. Moreover, in AF moieties the rotamer distribution around torsion angle gamma (O5'-C5'-C4'-C3') and the base orientation are influenced to a large extent by the presence of the fluorine substituent. The sugar rings of nonfluorinated residues in the trimers appear rather flexible. A possible correlation between the conformational characteristics of the fluorinated fragments and their biological activity has been found: the fragments that meet the prerequisites for binding to RNase L indeed show enhanced binding to this endonuclease. Furthermore, substitution of the 3'-OH group of the second residue by hydrogen or of the 3'-OH group of the 2'-terminal residue by fluorine or hydrogen results in increased resistance towards 2'-5'-phosphodiesterase.
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PMID:Conformation analysis of 3'-fluorinated A(2'-5')A(2'-5')A fragments. Relation between conformation and biological activity. 817 55

Incorporation of fluorine into proteins has long served as a means of probing structure and function, yet there are few studies that examine the impact of fluorine substitution, particularly at locations distant from the active sites of enzymes. The flexibility of isomeric fluorine incorporation at Phe is used to explore subtle substitution effects on enzyme activity and conformation. The unnatural amino acids o-, m-, and p-fluorophenylalanines were incorporated biosynthetically into the representative PvuII restriction endonuclease. Interestingly, m-fluoro-Phe-PvuII endonuclease exhibits very similar conformational stability to that of the native enzyme, but it exhibits a reproducible, 2-fold higher average specific activity. Given the level of incorporation and the distribution of species, the species of modified enzyme responsible for this increase in specific activity is most likely even faster. Further, moving the fluorine atom from the meta- to the para-position of Phe results in a 4-fold decrease in specific activity and a decrease in conformational stability of 1.5 kcal/mol. Since none of the Phe residues in PvuII endonuclease lies near the DNA recognition or catalytic sites, this differential behavior alludes to the impact of subtle changes in enzyme conformation on endonuclease activity and suggests novel ways to influence catalytic behavior.
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PMID:Differential effects of isomeric incorporation of fluorophenylalanines into PvuII endonuclease. 1153 60

Short interfering RNA (siRNA) duplexes are currently being evaluated as antisense agents for gene silencing. Chemical modification of siRNAs is widely expected to be required for therapeutic applications in order to improve delivery, biostability and pharmacokinetic properties. Beyond potential improvements in the efficacy of oligoribonucleotides, chemical modification may also provide insight into the mechanism of mRNA downregulation mediated by the RNA-protein effector complexes (RNA-induced silencing complex or RISC). We have studied the in vitro activity in HeLa cells of siRNA duplexes against firefly luciferase with substitutions in the guide strand of U for the apolar ribo-2,4-difluorotoluyl nucleotide (rF) [Xia, J. et al. (2006) ACS Chem. Biol., 1, 176-183] as well as of C for rF. Whereas an internal rF:A pair adjacent to the Ago2 ('slicer' enzyme) cleavage site did not affect silencing relative to the native siRNA duplex, the rF:G pair and other mismatches such as A:G or A:A were not tolerated. The crystal structure at atomic resolution determined for an RNA dodecamer duplex with rF opposite G manifests only minor deviations between the geometries of rF:G and the native U:G wobble pair. This is in contrast to the previously found, significant deviations between the geometries of rF:A and U:A pairs. Comparison between the structures of the RNA duplex containing rF:G and a new structure of an RNA with A:G mismatches with the structures of standard Watson-Crick pairs in canonical duplex RNA leads to the conclusion that local widening of the duplex formed by the siRNA guide strand and the targeted region of mRNA is the most likely reason for the intolerance of human Ago2 (hAgo2), the RISC endonuclease, toward internal mismatch pairs involving native or chemically modified RNA. Contrary to the influence of shape, the thermodynamic stabilities of siRNA duplexes with single rF:A, A:A, G:A or C:A (instead of U:A) or rF:G pairs (instead of C:G) show no obvious correlation with their activities. However, incorporation of three rF:A pairs into an siRNA duplex leads to loss of activity. Our structural and stability data also shed light on the role of organic fluorine as a hydrogen bond acceptor. Accordingly, UV melting (T(M)) data, osmotic stress measurements, X-ray crystallography at atomic resolution and the results of semi-empirical calculations are all consistent with the existence of weak hydrogen bonds between fluorine and the H-N1(G) amino group in rF:G pairs of the investigated RNA dodecamers.
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PMID:Crystal structure, stability and in vitro RNAi activity of oligoribonucleotides containing the ribo-difluorotoluyl nucleotide: insights into substrate requirements by the human RISC Ago2 enzyme. 1788 74

C2-Fluoro substituted DC-81, and its dimers that comprise of two C2-fluoro substituted DC-81 subunits tethered to their C8-position through simple alkane spacers as well as piperazine moiety side-armed with symmetrical alkyloxy spacers have been designed and synthesized. These fluoro substituted pyrrolo[2,1-c][1,4]benzodiazepines have shown remarkable DNA-binding ability and most of them possess promising anticancer activity, having GI(50) values in micromolar to nanomolar concentration range. DNA thermal denaturation studies show that some of these compounds (14a-c and 15) increase the DeltaT(m) values in the range of 28.9-38 degrees C, and this is further confirmed by the restriction endonuclease studies. This study illustrates the importance of introducing fluoro substitution at the C2-position apart from the incorporation of a piperazine ring in between the alkyloxy linker for enhancement of the DNA-binding ability in comparison to DSB-120 and SJG-136 (DeltaT(m)=10.2 and 25.7 degrees C). Moreover, the variations in the DNA-binding ability with respect to fluoro substitution in this class of dimers has been investigated by molecular modeling studies. Some representative C2-fluoro substituted dimers (8a and 14a) have also exhibited significant anticancer activity in the 60 cancer cell line assay of the National Cancer Institute (NCI).
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PMID:Remarkable enhancement in the DNA-binding ability of C2-fluoro substituted pyrrolo[2,1-c][1,4]benzodiazepines and their anticancer potential. 1916 61