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)

The fate of [3H]DNA from Streptococcus sanguis str-r43 fus-s donors in [14C]S. sanguis str-s fus-r1 recipients was studied by examining the lysates prepared from such recipients at various times after 1 min of exposure to DNA. The lysates were analyzed in CsCl and 10 to 30% sucrose gradients; fractions from the gradients were tested for biological activity and sensitivity to nucleases, subjected to various treatments and retested for nuclease sensitivity, and run on 5 to 20% neutral and alkaline sucrose gradients. The results demonstrate that donor DNA bound to S. sanguis cells in a form resistant to exogenous deoxyribonuclease is initially single stranded and complexed to recipient material. Donor DNA can be removed from the complex upon treatment of the complex with Pronase, phenol, or isoamyl alcohol-chloroform. Within the complex, donor DNA is relatively insensitive to S1 endonuclease but can regain its sensitivity by treatment with phenol. With time the complex moves as a whole to associate physically with the recipient chromosome. After a noncovalent stage of synapsis, donor material is covalently bonded to and acquires the nuclease sensitivity of recipient DNA, while donor markers regain transforming activity and become linked to resident markers.
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PMID:Fate of homospecific transforming DNA bound to Streptococcus sanguis. 64 Oct 7

An endodeoxyribonuclease has been purified 750-fold from human KB cells. The purified endonuclease requires Mg2+ for maximum activity: Mn2+ was less than half as active and Ca2+ inhibited the reaction. The optimum pH is 8.8 in Tris-HCl and the optimum buffer concentration is 10 mM. KCl (and NaCl), --SH-reacting reagents, and tRNA strongly inhibit the reaction. An apparent molecular weight of 54,000 was determined by sedimentation in a glycerol gradient. The purified endonuclease cleaved native, double-stranded adenovirus 2 DNA, and the reaction proceeded stepwise during the initial stage of degradation by cleavage of the DNA substrate in half, then in half again, etc. At longer digestion times, single strand scissions were detected. RNA was not a substrate for the enzyme. Poly(dG) . poly(dC) was susceptible but poly(dA) . poly(dT) was resistant to degradation. Hydrolysis of adenovirus 2 DNA yielded double-stranded polynucleotides containing 5'-phosphoryl and 3'-hydroxyl termini with short, single-stranded regions presumably at the ends. More than 50% of the product of a limit digest had a chain length greater than 35 to 40 nucleotides. Analysis of the 5' and 3' end groups of the digestion products indicated a preference for the site of the enzymatic cleavage; thymidylic acid residues were present at the 5' end and deoxyguanosine residues at the 3' end, each with a frequency of 40 to 50%.
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PMID:An endodeoxyribonuclease of human KB cells. Purification and properties of the enzyme. 64 80

The incidence of pyrimidine dimer formation and the kinetics of DNA repair in African green monkey kidney CV-1 cells after ultraviolet (UV) irradiation were studied by measuring survival, T4 endonuclease V-sensitive sites, the fraction of pyrimidine dimers in acid-insoluble DNA as determined by thin layer chromatography (TLC), and repair replication. CV-1 cells exhibit a survival curve with extrapolation number n = 7.8 and Do = 2.5 J/m2. Pyrimidine dimers were lost from acid-insoluble DNA more slowly than endonuclease-sensitive sites were lost from or new bases were incorporated into high molecular weight DNA during the course of repair. Growth of CV-1 cultures in [3H]thymidine or X-irradiation (2 or 10 krads) 24 h before UV irradiation had no effect on repair replication induced by 25 J/m2 of UV. These results suggest that pyrimidine dimer excision measurements by TLC are probably unaffected by radiation from high levels of incorporated radionuclides. The endonuclease-sensitive site and TLC measurements can be reconciled by the assumption that pyrimidine dimers are excised from high molecular weight DNA in acid-insoluble oligonucleotides that are slowly degraded to acid-soluble fragments.
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PMID:Excision repair of ultraviolet damage in mammalian cells. Evidence for two steps in the excision of pyrimidine dimers. 65 44

We have used a T4 endonuclease V assay method for UV-induced pryrimidine dimers in cellular DNA in vivo to obtain evidence for recombinational DNA exhanges after UV irradiation of normal human and Xeroderma pigmentosum (XP) cells. Our data indicate that the endonuclease-sensitive sites in excision-defective XP cells are removed very slowly from the irradiated parental strands and appear concomitantly in daughter strands newly synthesized during post-UV incubation. In the defective XP cells, the extent of appearance of sensitive sites in daughter strands synthesized during a period of 24 h after 10 J/m2 appears to be small, probably less than 15% of the initial number of sensitive sites detected in cellular parental strands. Demonstration of such exchanges between normal-density parental and 5-bromodeoxyuridine-labeled daughter strands by alkaline CsCl isopycnic centrifugation was unsuccessful. Further, the extent is much lower in normal human cells because of their efficient excision repair of the dimers before and after exchanges than in the defective XP cells.
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PMID:Low-level DNA exchanges in normal human and xeroderma pigmentosum cells after UV irradiation. 86 96

The Mg-2+-Sarkosyl crystals (M band) procedure was used to study the effect of ribonuclease (RNase) A on the association of Escherichia coli deoxyribonucleic acid (DNA) with membrane. Incubation of gently prepared cell extracts with RNase results in the release of DNA from membrane. This effect appears to result from the activation, by RNase, of endonuclease I and subsequent limited activity of this deoxyribonuclease. In support of this explanation, it is demonstrated (i) that the extent of the RNase-induced loss of DNA from membrane is directly correlated with the endogenous level of endonuclease I, and (ii) that endonucleolytic activity occurs when gently lysed cell preparations are incubated in the presence of RNase.
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PMID:Effect of ribonuclease on the association of deoxyribonucleic acid with the membrane in Escherichia coli. 109 60

Human cells prelabeled with [32P]phosphate were exposed to UV and then pulse-labeled with [3H]thymidine. The DNA from these cells was subsequently treated with T4 endonuclease V, an enzyme which specifically nicks DNA at positions adjacent to pyrimidine dimers. Sedimentation in alkaline sucrose gradients revealed that both the DNA made before and that made after irradiation contained nuclease-sensitive sites, indicating that a recombinational process between these DNAs might be occurring during postirradiation incubation. Sedimentation in neutral sucros gradients showed that the molecular weight of native DNA remained unchanged for both DNAs upon endonuclease treatment, indicating that gaps opposite dimers are not necessarily formed after irradiation.
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PMID:Postreplication repair in human cells: on the presence of gaps opposite dimers and recombination. 119 Nov 86

The recently isolated neutral deoxyribonuclease from crab (Cancer pagurus) testes has been characterized in its mode of action and its specificity. The enzyme is a typical endonuclease, forming 5'-phosphate oligonucleotides of large average size; after extensive digestion of calf thymus DNA over 75% of the fragments have a size larger than pentanucleotides and mononucleotides are absent. As far as specificity is concerned, thymidine is very abundant in the 5'-penultimate position (approximately 50%) and in the 3'-terminal position (37%) and almost absent in the 5'-terminal position (approximately 1%), the values quoted concerning Escherichia coli digests of average size (Pn) between 50 and 10.
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PMID:The specificity of a neutral deoxyribonuclease from Cancer pagurus. 123 41

T4 endonuclease V catalyzes the hydrolysis of the glycosyl bond of a thymine dimer in a DNA duplex and the cleavage of the 3'-phosphate by beta-elimination. We have previously identified a catalytic site for the first reaction (pyrimidine dimer-glycosylase activity) by systematic mutagenesis (Doi et al. Proc. Natl. Acad. Sci. USA 1992 in press) and by x-ray crystallography (Morikawa et al. Science, 256: 523-526, 1992). The results showed that replacement of Glu23 with either glutamine or aspartic acid completely abolished the glycosylase activity. We describe the investigation of the second reaction (apurinic/apyrimidinic endonuclease activity), using twenty two mutants of T4 endonuclease V plus a DNA mini duplex containing an abasic site. Replacement of Glu23 by glutamine abolished the second reaction, but replacement with aspartic acid did not. The pH optima of the mutant (23 Asp) and the wild type were found to be 5.0 and 5.5, respectively. We conclude that the carboxylate anion in position 23 may act as a general base in the beta-elimination reaction of the endonuclease.
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PMID:Participation of glutamic acid 23 of T4 endonuclease V in the beta-elimination reaction of an abasic site in a synthetic duplex DNA. 135 29

Exposing the skin of mice to UV radiation interferes with the induction of delayed and contact hypersensitivity immune responses initiated at nonirradiated sites. The identity of the molecular target in the skin for these immunosuppressive effects of UV radiation remains controversial. To test the hypothesis that DNA is the target for UV-induced systemic immunosuppression, we exposed C3H mice to UV radiation and then used liposomes to deliver a dimer-specific excision repair enzyme into the epidermis in situ. The application of T4 endonuclease V encapsulated in liposomes to UV-irradiated mouse skin decreased the number of cyclobutane pyrimidine dimers in the epidermis and prevented suppression of both delayed and contact hypersensitivity responses. Moreover, the formation of suppressor lymphoid cells was inhibited. Control, heat-inactivated endonuclease encapsulated in liposomes had no effect. These studies demonstrate that DNA is the major target of UV radiation in the generation of systemic immunosuppression and suggest that the primary molecular event mediating these types of immunosuppression by UV radiation is the formation of pyrimidine dimers. Furthermore, they illustrate that the delivery of lesion-specific DNA repair enzymes to living skin after UV irradiation is an effective tool for restoring immune function and suggest that this approach may be broadly applicable to preventing other alterations caused by DNA damage.
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PMID:Pyrimidine dimers in DNA initiate systemic immunosuppression in UV-irradiated mice. 150 62

The x-ray structure of T4 endonuclease V, an enzyme responsible for the first step of a pyrimidine-dimer-specific excision-repair pathway, was determined at a 1.6-angstrom resolution. The enzyme consists of a single compact domain classified into an all-alpha structure. This single domain has two distinct catalytic activities; it functions as a pyrimidine dimer glycosylase and as an apurinic-apyrimidinic endonuclease. The amino-terminal segment penetrates between two major helices and prevents their direct contact. The refined structure suggests the residues involved in the substrate binding and the catalysis of the glycosylation reaction.
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PMID:X-ray structure of T4 endonuclease V: an excision repair enzyme specific for a pyrimidine dimer. 157 27


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