Abasic (AP) sites in DNA arise from spontaneous reactions or the action of DNA glycosylases and represent a loss of genetic information. The AP sites can be mutagenic or cytotoxic, and their repair is initiated by class II AP endonucleases, which incise immediately 5' to AP sites. The main enzyme of S. cerevisiae. Apn1, provides ...

Defined DNA substrates containing discrete abasic sites or paired abasic sites set 1, 3, 5 and 7 bases apart on opposite strands were constructed to examine the reactivity of S1, mung bean and P1 nucleases towards abasic sites. None of the enzymes acted on the substrate containing discrete abasic sites. Under ...

M and 10 s 1 , respectively. Heat treatment of the abasic site-containing 49-mer without enzyme also bound tightly to DNA containing an abasic site and formed a 1:1 complex at low enzyme concentrations.1.25.2) is a bifunctional enzyme with the ability both to initiate repair of abasic sites in damaged DNA and to act

The loss of bases from cellular DNA occurs via both spontaneous and mutagen-induced reactions. The resulting apurinic/apyrimidinic (AP) sites are cytotoxic and mutagenic but are counteracted by repair initiated by AP endonucleases. Previously, in vitro and bacterial transfection studies suggested that AP sites often prompt insertion of dAMP residues during replication, the ...

Escherichia coli endonuclease IV is an archetype for an abasic or apurinic-apyrimidinic endonuclease superfamily crucial for DNA base excision repair. Here biochemical, mutational and crystallographic characterizations reveal a three-metal ion mechanism for damage binding and incision. The 1.10-{angstrom} resolution DNA-free and the ...

The C2?-oxidized abasic lesion (C2-AP) is produced in DNA that is subjected to oxidative stress. The lesion disrupts replication and gives rise to mutations that are dependent upon the identity of the upstream nucleotide. Ape1 incises C2-AP, but the 5?-phosphorylated fragment is not a substrate for the lyase activity of DNA polymerase ? (Pol ?). Excision of the lesion is ...

Lecture I - Restriction Endonucleases by B. Howard, NIH, describes action of restriction endonucleases, nomenclature, availability of these materials, and certain difficulties. Lecture II - Variable Number Tandem Repeats (VNTR) by S. Odelberg, University ...

Aerobic respiration generates reactive oxygen species (ROS) as a by-product of cellular metabolism which can damage DNA. The complex nature of oxidative DNA damage requires actions of several repair pathways. Oxidized DNA bases are substrates for two overlapping pathways: base excision repair (BER) and nucleotide incision repair (NIR). In the BER pathway a DNA glycosylase ...

Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) has diverse biological functions including its nuclear translocation in response to oxidative stress. We show that GAPDH physically associates with APE1, an essential enzyme involved in the repair of abasic sites in damaged DNA, as well as in the redox regulation of several transcription factors. This interaction allows ...

Endonuclease V (deoxyinosine 3? endonuclease), the product of the nfi gene, has a specificity that encompasses DNAs containing dIMP, abasic sites, base mismatches, uracil, and even untreated single-stranded DNA. To determine its importance in DNA repair pathways, nfi insertion mutants and overproducers (strains bearing nfi plasmids) ...

Three genes that participate in the repair of DNA alkylation damage were recently cloned from Saccharomyces cerevisiae: the MGT1 O6-methylguanine DNA methyltransferase gene, the MAG 3-methyladenine DNA glycosylase gene, and the APN1 apurinic/apyrimidinic (AP) endonuclease gene. Altering the expression levels of these three genes produced significant changes in the S. ...

One of the most frequent lesions formed in cellular DNA are abasic (apurinic/apyrimidinic, AP) sites that are both cytotoxic and mutagenic, and must be removed efficiently to maintain genetic stability. It is generally believed that the repair of AP sites is initiated by the AP endonucleases; however, an alternative pathway seems to prevail in ...

The N-glycosidic bond can be hydrolyzed spontaneously or by glycosylases during removal of damaged bases by the base excision repair pathway, leading to the formation of highly mutagenic apurinic/apyrimidinic (AP) sites. Organisms encode for evolutionarily conserved repair machinery, including specific AP endonucleases that cleave the DNA backbone 5? to the AP site to prime ...

Abasic (AP) sites are common, potentially mutagenic DNA damages that are attacked by AP endonucleases. The biological roles of these enzymes in metazoans have not been tested. We have cloned the human cDNA (APE) that encodes the main nuclear AP endonuclease. The predicted Ape protein, which contains likely nuclear transport signals, is ...

Abasic (AP) sites are common, potentially mutagenic DNA damages that are attacked by AP endonucleases. The biological roles of these enzymes in metazoans have not been tested. The authors have cloned the human cDNA (APE) that encodes the main nuclear AP endonuclease. The predicted Ape protein, which contains likely nuclear transport ...

Clustered damage in DNA includes two or more closely spaced oxidized bases, strand breaks or abasic sites that are induced by high- or low-linear-energy-transfer (LET) radiation, and these have been found to be repair-resistant and potentially mutagenic. In the present study we found that abasic clustered damages are also induced in primary human ...

Loss of a base in DNA, i.e., creation of an abasic site leaving a deoxyribose residue in the strand, is a frequent lesion that may occur spontaneously, or under the action of radiations and alkylating agents, or enzymatically as an intermediate in the repair of modified or abnormal bases. The abasic site lesion is mutagenic or lethal ...

Apurinic/apyrimidinic endonuclease 1 (APE1) is the major mammalian enzyme in DNA base excision repair that cleaves the DNA phosphodiester backbone immediately 5' to abasic sites. Recently, we identified APE1 as an endoribonuclease that cleaves a specific coding region of c-myc mRNA in vitro, regulating c-myc mRNA level and half-life in cells. Here, we ...

The abasic (AP) sites, the major mutagenic and cytotoxic genomic lesions, induced directly by oxidative stress and indirectly after excision of damaged bases by DNA glycosylases, are repaired by AP-endonucleases (APEs). Among two APEs in Saccharomyces cerevisiae, Apn1 provides the major APE activity, and Apn2, the ortholog of the mammalian APE, provides ...

The abasic (AP) sites, the major mutagenic and cytotoxic genomic lesions, induced directly by oxidative stress and indirectly after excision of damaged bases by DNA glycosylases, are repaired by AP-endonucleases (APEs). Among two APEs in Saccharomyces cerevisiae, Apn1 provides the major APE activity, and Apn2, the ortholog of the mammalian APE, provides ...

Hydrogen bonded histidineaspartate (HisAsp) pairs are critical constituents in several key enzymatic reactions. To date, the role that these pairs play in catalysis is best understood in serine and trypsin-like proteases, where structural and biochemical NMR studies have revealed important pKa values and hydrogen bonding patterns within the catalytic pocket. However, the role of the HisAsp pair in ...

Hydrogen bonded histidine-aspartate (His-Asp) pairs are critical constituents in several key enzymatic reactions. To date, the role that these pairs play in catalysis is best understood in serine and trypsin-like proteases, where structural and biochemical NMR studies have revealed important pKa values and hydrogen-bonding patterns within the catalytic pocket. However, the role of the His-Asp ...

To elucidate the mechanism of interaction of restriction endonuclease EcoRII with DNA, we studied by

Mutagenic abasic (AP) sites are generated directly by DNA-damaging agents or by DNA glycosylases acting in base excision repair. AP sites are corrected via incision by AP endonucleases, removal of deoxyribose 5-phosphate, repair synthesis, and ligation. Mammalian DNA polymerase ? (Pol?) carries out most base excision repair synthesis and also can excise ...

A DNAzyme, synthetically modified with both primary amines and imidazoles, is found to act as a M2+ -independent AP lyase-endonuclease. In the course of the cleavage reaction, this DNAzyme forms a covalent Schiff base intermediate with an abasic site on a complementary oligodeoxyribonucleotide. This intermediate, which is inferred from NaCNBH3 trapping as ...

The action of an endonuclease from Micrococcus luteus that operates on uv damage in DNA overlaps with that of DNA photolyase from yeast: homo- and heterocyclobutane dipyrimidines in DNA are substrates for both enzymes, but pyrimidine adducts or the spore photoproduct in DNA are not. As expected from this overlap, the action of ...

The base excision repair (BER) pathway repairs a wide variety of damaged nucleobases in DNA. This pathway is initiated by a DNA repair glycosylase, which locates the site of damage and catalyzes the excision of the damaged nucleobase. The resulting abasic site is further processed by apurinic/apyrimidinic site endonuclease 1 (APE1) to create a single ...

Oxidized abasic residues in DNA constitute a major class of radiation and oxidative damage. Free radical attack on the nucleotidyl C-1' carbon yields 2-deoxyribonolactone (dL) as a significant lesion. Although dL residues are efficiently incised by the main human abasic endonuclease enzyme Ape1, we show here that subsequent excision by ...

The recognition of 'regular' and 'oxidized' sites of base loss (AP sites) in DNA by various AP endonucleases was compared. Model substrates with regular AP sites (resulting from mere hydrolysis of the glycosylic bond) were produced by damaging bacteriophage PM2 DNA by exposure to low pH; those with AP sites oxidized at the C-4'- and C-1'-position of the sugar moiety by ...

Micrococcus luteus extracts contain ..gamma..-endonuclease, a Mg/sup 2 +/-independent endonuclease that cleaves ..gamma..-irradiated DNA. This enzyme has been purified approximately 1000-fold, and the purified enzyme was used to study its substrate specificity and mechanism of action. ..gamma..-Endonuclease cleaves ...

The Apn2 protein of Saccharomyces cerevisiae contains 3??5? exonuclease and 3?-phosphodiesterase activities, and these activities function in the repair of DNA strand breaks that have 3?-damaged termini and which are formed in DNA by the action of oxygen-free radicals. Apn2 also has an AP endonuclease activity and functions in the removal of ...

Base excision repair (BER) is a critical pathway in cellular defense against endogenous or exogenous DNA damage. This elaborate multistep process is initiated by DNA glycosylases that excise the damaged base, and continues through the concerted action of additional proteins that finally restore DNA to the unmodified state. BER has been subject to detailed biochemical analysis ...

There is increasing evidence that UVA radiation, which makes up ?95% of the solar UV light reaching the Earth's surface and is also commonly used for cosmetic purposes, is genotoxic. However, in contrast to UVC and UVB, the mechanisms by which UVA produces various DNA lesions are still unclear. In addition, the relative amounts of various types of UVA lesions and their mutagenic significance are ...

Implementation of proper analytical tool for systematic investigation and quantitative determination of different classes of cadmium ion-induced DNA damages, especially at low metal ion concentrations, is still lacking. Using lesion-specific enzymes that cleave DNA at specific classes of damage and a fluorometric approach developed for quantifying fluorophore-labeled oligonucleotides bound to chip ...

Activation-induced deaminase (AID) initiates diversity of immunoglobulin genes through deamination of cytosine to uracil. Two opposing models have been proposed for the deamination of DNA or RNA by AID. Although most data support DNA deamination, there is no physical evidence of uracil residues in immunoglobulin genes. Here we demonstrate their presence by determining the sensitivity of DNA to ...

DNA sequences determined from ancient organisms have high error rates, primarily due to uracil bases created by cytosine deamination. We use synthetic oligonucleotides, as well as DNA extracted from mammoth and Neandertal remains, to show that treatment with uracil-DNA-glycosylase and endonuclease VIII removes uracil residues from ancient DNA and repairs most of the resulting ...

DNA sequences determined from ancient organisms have high error rates, primarily due to uracil bases created by cytosine deamination. We use synthetic oligonucleotides, as well as DNA extracted from mammoth and Neandertal remains, to show that treatment with uracil�DNA�glycosylase and endonuclease VIII removes uracil residues from ancient DNA and repairs most of the ...

Here we describe a novel endonuclease IV (Endo IV) based assay utilizing a substrate that mimics the abasic lesions that normally occur in double-stranded DNA. The three component substrate is characterized by single-stranded DNA target, an oligonucleotide probe, separated from a helper oligonucleotide by a one base gap. The oligonucleotide probe contains ...

Chromosomal rearrangements and base substitutions contribute to the large intraspecies genetic diversity of Helicobacter pylori. Here we explored the base excision repair pathway for the highly mutagenic 8-oxo-7,8-dihydroguanine (8-oxoG), a ubiquitous form of oxidized guanine. In most organisms, 8-oxoG is removed by a specific DNA glycosylase (Fpg in bacteria or OGG1 in eukaryotes). In the case ...

APE1/Ref-1 (hereafter, APE1), a DNA repair enzyme and a transcriptional coactivator, is a vital protein in mammals. Its role in controlling cell growth and the molecular mechanisms that fine-tune its different cellular functions are still not known. By an unbiased proteomic approach, we have identified and characterized several novel APE1 partners which, unexpectedly, include a number of proteins ...

Activation-induced cytidine deaminase (AID) is believed to initiate somatic hypermutation (SHM) by deamination of deoxycytidines to deoxyuridines within the immunoglobulin variable regions genes. The deaminated bases can subsequently be replicated over, processed by base excision repair or mismatch repair, leading to introduction of different types of point mutations (G/C transitions, G/C ...

The study aimed to elucidate the action and biological functions of a site-specific endonuclease discovered in yeast, for use as a genetic tool. The authors characterized the specific I-SceI endonuclease and used it to induce in vivo recombinations. Their...

Abasic (AP) sites in DNA are potentially lethal and mutagenic. 'Class II' AP endonucleases initiate the repair of these and other DNA lesions. In yeast, the predominant enzyme of this type is Apn1, and its elimination sensitizes the cells to killing by simple alkylating agents or oxidants, and raises the rate of spontaneous mutation. We investigated the ...

The homing endonuclease I-Ssp6803I causes the insertion of a group I intron into a bacterial tRNA gene�the only example of an invasive mobile intron within a bacterial genome. Using a computational fold prediction, mutagenic screen and crystal structure determination, we demonstrate that this protein is a tetrameric PD-(D/E)-XK endonuclease�a fold ...

RNase III of Escherichia coli is the endonuclease responsible for the first steps in the post-transcriptional processing of E. coli ribosomal RNA. The purification and structure of RNase III are discussed. The action of RNase III in cleaving double-strand...

RNase III of Escherichia coli is the endonuclease responsible for the first steps in the post-transcriptional processing of E. coli ribosomal RNA. The purification and structure of RNase III are discussed. The action of RNase III in cleaving double-stranded and single-stranded RNA is briefly reviewed. (ACR)

Using bacteria as a model, the molecular basis of the mutagenic and lethal effects of uv radiation is being studied. Attention is focused on the mechanism of action of uv-1 specific endonucleases in the repair of damaged DNA. The isolation and identificat...

We have been investigating two DNA-dependent ATPases from Escherichia coli, the type-I restriction endonuclease from E. coli B (EcoB) and exonuclease V (the recBC enzyme) of E. coli K12. This paper summarizes the results of our most recent studies of the mechanisms of action of these enzymes in vitro and attempts to relate these mechanisms to in vivo ...

The second enzyme in the DNA base excision repair (BER) pathway, apurinic/apyrimidinic (AP) endonuclease or Ape1, hydrolyzes the phosphodiester backbone immediately 5' to an AP site generating a normal 3'-hydroxyl group and an abasic deoxyribose-5-phosphate, which is processed by subsequent enzymes of the BER pathway. AP sites are the most common form of ...

To examine mammalian base excision repair (BER) enzymes interacting with DNA intermediates formed during BER, we used a novel photoaffinity labeling probe and mouse embryonic fibroblast (MEF) crude extract. The probe was formed in situ, using an end-labeled oligonucleotide containing a synthetic abasic site; this site was incised by AP endonuclease ...

APE1 is the major nuclease for excising abasic (AP) sites and particular 3'-obstructive termini from DNA, and is an integral participant in the base excision repair (BER) pathway. BER capacity plays a prominent role in dictating responsiveness to agents that generate oxidative or alkylation DNA damage, as well as certain chain-terminating nucleoside analogs and 5-fluorouracil. ...

APE1 is the major nuclease for excising abasic (AP) sites and particular 3?-obstructive termini from DNA, and is an integral participant in the base excision repair (BER) pathway. BER capacity plays a prominent role in dictating responsiveness to agents that generate oxidative or alkylation DNA damage, as well as certain chain-terminating nucleoside analogs and 5-fluorouracil. ...

The base excision repair (BER) pathway recognizes and repairs most nonbulky lesions, uracil and abasic (AP) sites in DNA. Several participants are embryonic lethals in knockout mice. Since the pathway has never been investigated during embryogenesis, we characterized the first three steps of BER in zebrafish extracts from unfertilized eggs, embryos at different developmental ...

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Recent studies have shown purified preparations of phage T4 UV DNA-incising activity (T4 UV endonuclease or endonuclease V of phage T4) contain a pyrimidine dimer-DNA glycosylase activity that catalyzes hydrolysis of the 5' glycosyl bond of dimerized pyrimidines in UV-irradiated DNA. Such enzyme preparations have also been shown to catalyze the hydrolysis ...

... Accession Number : ADA081346. Title : ZMOB: A Mob of 256 Cooperative Z80A-Based Microcomputers. Descriptive Note : Technical rept.,. ...

... Accession Number : ADD520288. Title : ZMOB: A Mob of 256 Cooperative 280A-Based Microcomputers. Descriptive Note : Conference paper,. ...

... pyrimidine oligodeoxyribonucleotides is limited to mostly purine tracts (TAT, ... pyrimidine bases and abasic residues when placed across each other. ...

Using isogenic mouse embryonic fibroblasts and human cancer cell lines, we show that cells defective in base excision repair (BER) display a cisplatin-specific resistant phenotype. This was accompanied by enhanced repair of cisplatin interstrand cross-links (ICLs) and ICL-induced DNA double strand breaks, but not intrastrand adducts. Cisplatin induces abasic sites with a ...

AbstractThe DNA base excision repair (BER) pathway repairs alkylation and oxidative DNA damage caused by endogenous and exogenous agents, including chemotherapeutic agents. Upon removal of the damaged base AP endonuclease 1 (Ape1), a critical component of the pathway cleaves the abasic site to facilitate repair. Ape1 is a multifunctional protein which ...

Reactive oxygen species, generated endogenously and induced as a toxic response, produce several dozen oxidized or modified bases and/or single-strand breaks in mammalian and other genomes. These lesions are predominantly repaired via the conserved base excision repair (BER) pathway. BER is initiated with excision of oxidized or modified bases by DNA glycosylases leading to formation of ...

Apurinic/apyrimidinic endonuclease 1 (APE1), an essential protein in mammals, is involved in base excision DNA repair (BER) and in regulation of gene expression, acting as a redox co-activator of several transcription factors. Recent findings highlight a novel role for APE1 in RNA metabolism, which is modulated by nucleophosmin (NPM1). The results reported in this article show ...

The overall objective of this project has been to develop immunochemical methods to quantitate unique DNA base damages in order to facilitate studies on radiation-induced damage production and repair. Specifically, we have been using antibodies raised to damaged bases to quantitate unique lesions in model systems in order to evaluate their potential biological consequences. Our approach has been ...

The overall objective of this project has been to develop immunochemical methods to quantitate unique DNA base damages in order to facilitate studies on radiation-induced damage production and repair. Specifically, we have been using antibodies raised to damaged bases to quantitate unique lesions in model systems in order to evaluate their potential biological consequences. Our approach has been ...

Bacteria evolved restriction endonucleases to prevent interspecies DNA transmission and bacteriophage infection. Here, we show that human cells possess an analogous mechanism. APOBEC3A is induced by interferon following DNA detection, and it deaminates foreign double-stranded DNA cytidines to uridines. These atypical DNA nucleosides are converted by the uracil DNA glycosylase ...

Immunoglobulin class switch recombination (CSR) occurs by an intrachromosomal deletion requiring generation of double-stranded DNA breaks (DSBs) in immunoglobulin switch region DNA. The initial steps of DSB formation have been elucidated: cytosine deamination by activation-induced cytidine deaminase (AID) and the generation of abasic sites by uracil-DNA glycosylase (UNG). We ...

Endonuclease VIII (Nei) is a DNA glycosylase of the base excision repair pathway that recognizes and excises oxidized pyrimidines. We determined the crystal structures of a NEIL1 ortholog from the giant Mimivirus (MvNei1) unliganded and bound to DNA containing tetrahydrofuran (THF), which is the first structure of any Nei with an abasic site analog. The ...

Ionizing radiation produces a distinctive pattern of bistranded clustered lesions in DNA. A relatively low number of clustered lesions may be lethal to cells when compared to a larger number of single lesions. Enzyme cleavage experiments suggest that the orientation of bistranded lesions causes differential recognition and removal of these lesions. Like that of a previous study of bistranded ...

Abasic [apurinic/apyrimidinic (AP)] sites are common, noncoding DNA lesions. Despite extensive investigation, the mutational pattern they provoke in eukaryotic cells remains unresolved. We constructed Saccharomyces cerevisiae strains in which chromosomal AP sites were generated during normal cell growth by altered human uracil-DNA glycosylases that remove undamaged cytosines ...

In Saccharomyces cerevisiae, the base excision DNA repair (BER) pathway has been thought to involve only a multinucleotide (long-patch) mechanism (LP-BER), in contrast to most known cases that include a major single-nucleotide pathway (SN-BER). The key step in mammalian SN-BER, removal of the 5'-terminal abasic residue generated by AP endonuclease ...

The {alpha} anomer of deoxyadenosine ({alpha}) and an abasic site (tetrahydrofuran, F), which are DNA lesions produced by free radical. were site-specifically incoorporated in 9-mer duplexes d (TGAGXGTAC)d-(GTACNCTCA), where X-{alpha} or F and N=A,G,C, or, T. Their influence on thermodynamic stability and structure of DNA was assessed by UV-melting measurements and molecular ...

The endonuclease Argonaute2 (Ago2) mediates the degradation of the target mRNA within the RNA-induced silencing complex. We determined the binding and cleavage properties of recombinant human Ago2. Human Ago2 was unable to cleave preformed RNA duplexes and exhibited weaker binding affinity for RNA duplexes compared with the single strand RNA. The enzyme exhibited greater RNase ...

Abasic (AP) sites in DNA arise through both endogenous and exogenous mechanisms. Since AP sites can prevent replication and transcription, the cell contains systems for their identification and repair. AP endonuclease (APEX1) cleaves the phosphodiester backbone 5? to the AP site. The cleavage, a key step in the base excision repair pathway, is followed by ...

A key issue in studying mammalian DNA base excision repair is how its component proteins respond to a plethora of cell-signaling mediators invoked by DNA damage and stress-inducing agents such as reactive oxygen species, and how the actions of individual BER proteins are attributed to cell survival or apoptotic/necrotic death. This article reviews the past and recent progress ...

BackgroundThe development and regression of corpus luteum (CL) is characterized by an intense angiogenesis and angioregression accompanied by luteal tissue and extracellular matrix (ECM) remodelling. Vascular Endothelial Growth Factor (VEGF) is the main regulator of angiogenesis, promoting endothelial cell mitosis and differentiation. After the formation of neovascular tubes, the remodelling of ...

An endonuclease which is active upon DNA exposed to ultraviolet light at a photoproduct other than thymine dimers has been extensively purified from Escherichia coli. The small (2.7 S) enzyme is active in the presence of EDTA, has a neutral pH optimum, and is inhibited by tRNA and 1 M NaCl. It has no detectable exonuclease, DNA N-glycosidase, or ribonuclease activities. The ...

Partial depurination of d-ApA produced two UV260nm-absorbing isomers, d-SpA and d-ApS (where S represents the depurinated deoxyribose sugar), that provided simple model compounds with which to examine, by HPLC, the response of nucleases to phosphodiester bonds flanked 3' or 5' by an apurinic site. The structural identity of each compound was established by (i) reaction with methoxyamine to confirm ...

DNA glycosylases/AP lyases initiate repair of oxidized bases in the genomes of all organisms by excising these lesions and then cleaving the DNA strand at the resulting abasic (AP) sites and generate 3' phospho alpha,beta-unsaturated aldehyde (3' PUA) or 3' phosphate (3' P) terminus. In Escherichia coli, the AP-endonucleases (APEs) hydrolyze both 3' ...

Recently, we found an interaction between adenomatous polyposis coli (APC) and DNA polymerase ? (pol-?) and showed that APC blocks strand-displacement synthesis of long-patch base excision repair (LP-BER) however, the mechanism is not clear. Using an in vivo LP-BER assay system, we now show that the LP-BER is higher in APC^?/? cells than in APC^+/+ ...

Apurinic/apyrimidinic endonuclease 1 (APE1), a member of the divalent cation-dependent phosphoesterase superfamily of proteins that retain the conserved four-layered ?/?-sandwich structural core, is an essential protein that functions as part of base excision repair to remove mutagenic and cytotoxic abasic sites from DNA. Using low temperature solid-state ...

Base excision repair (BER) is an essential cellular defense against DNA damage, yet in plants is poorly understood. We used an assay that monitors repair of damaged bases and abasic (AP) sites in Arabidopsis to characterize post-excision events during plant BER. We found that ARP is the major AP endonuclease activity in Arabidopsis cell extracts, and is ...

DNA double-strand breaks (DSBs) are potent sources of genome instability. While there is considerable genetic and molecular information about the disposition of direct DSBs and breaks that arise during replication, relatively little is known about DSBs derived during processing of single-strand lesions, especially for the case of single-strand breaks (SSBs) with 3?-blocked termini generated in ...

Substrate specificities of FPG protein (also known as formamidopyrimidine DNA glycosylase) and 8-hydroxyguanine endonuclease were compared by using defined duplex oligodeoxynucleotides containing single residues of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG), 8-oxo-7,8-dihydro-2'-deoxyadenosine (8-oxodA), and 2,6-diamino-4-hydroxy-5-(N-methyl)formamidopyrimidine (Me-Fapy). ...

... Accession Number : AD0743446. Title : Sensitization of Deoxyribonucleic Acid to Endonuclease by Adenine Alkylation. ...

The major human apurinic/apyrimidinic (AP) endonuclease (class II) is known to cleave DNA 5? adjacent to an AP site, which is probably the most common DNA damage produced hydrolytically or by glycosylase-mediated removal of modified bases. p-Benzoquinone (pBQ), one of the major benzene metabolites, reacts with DNA to form bulky exocyclic adducts. Herein we report that ...

The UV endonucleases from Micrococcus luteus and bacteriophage T4 possess two catalytic activities specific for the site of cyclobutane pyrimidine dimers in UV-irradiated DNA: a DNA glycosylase that cleaves the 5'-glycosyl bond of the dimerized pyrimidines and an apurinic/apyrimidinic (AP) endonuclease that thereupon incises the phosphodiester ...

Ultraviolet (UV) irradiation produces a variety of damages to purine residues in DNA, which include photoalkylated purines, purine-pyrimidine photoadducts and adenine photodimers. In this study, an enzymatic activity which incises UV-irradiated DNA at sites of adenines was isolated from an Escherichia coli mutant. This endonuclease activity was purified 86-fold with a 28% ...

We show that total H1 histone from wheat seedlings or rat liver enhances hydrolysis of lambda phage DNA with plant endonucleases WEN1 and WEN2 isolated from wheat coleoptiles. Optimal DNA/protein weight ratio in the hydrolysis reaction is 1 : 1. The action of fractions I and IV (obtained from total wheat H1 histone by electrophoresis) on DNA hydrolysis ...

Nucleotide excision repair (NER) is a DNA repair pathway that is responsible for removing a variety of lesions caused by harmful UV light, chemical carcinogens, and environmental mutagens from DNA. NER involves the concerted action of over 30 proteins that sequentially recognize a lesion, excise it in the form of an oligonucleotide, and fill in the resulting gap by repair ...

The DNA duplexes shown below, with D indicating deoxyribose aldehyde abasic sites and numbering from 5{prime} to 3{prime}, have been investigated by NMR. The {sup 31}P-{sup 1}H correlation data indicate that the backbones of these duplex DNAs are regular. One- and two-dimensional {sup 1}H NMR data indicate that the duplexes are right-handed and B-form. Conformational changes ...

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The authors have determined the three-dimensional structure of a non-self-complementary oligodeoxynucleotide duplex that contains a model abasic site. The duplex contains six GC base pairs plus the abasic site at the center of one strand and corresponds to an abasic frameshift. Two-dimensional NMR studies on the nonexchangeable protons ...

For a long time it has been assumed that the decay of RNA in eukaryotes is mainly carried out by exoribonucleases, which is in contrast to bacteria, where endoribonucleases are well documented to initiate RNA degradation. In recent years, several as yet unknown endonucleases have been described, which has changed our view on eukaryotic RNA metabolism. Most importantly, it was ...

Current large scale genome mapping methodology suffers from a lack of tools for generating specific DNA fragments in the megabase size range. While technology such as pulsed field gel electrophoresis can resolve DNA fragments greater than 10 megabases in size, current methods for cleaving mammalian DNA using bacterial restriction enzymes are incapable of producing such fragments. Though several ...

We describe the synthesis of an abasic RNA phosphoramidite carrying a photocleavable 1-(2-nitrophenyl)ethyl (NPE) group at the anomeric center and a triisopropylsilyloxymethyl (TOM) group as 2'-O-protecting group together with the analogous DNA and the 2'-OMe RNA abasic building blocks. These units were incorporated into RNA-, 2'-OMe-RNA- and DNA for the ...

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Treatment of cells with oxidative DNA damaging agents such as ionizing radiation and hydrogen peroxide produces .OH radicals which attack DNA, producing single strand breaks and double strand breaks that have a 3'-blocked terminus with a phosphoglycolate or a phosphate group attached to the 3'-terminus. While DNA strand breaks with 3'-blocked termini are the hallmark of ...

OAK B202 Treatment of cells with oxidative DNA damaging agents such as ionizing radiation and hydrogen peroxide produces .OH radicals which attack DNA, producing single strand breaks and double strand breaks that have a 3'-blocked terminus with a phosphoglycolate or a phosphate group attached to the 3'-terminus. While DNA strand breaks with 3'-blocked termini are the ...

SummaryThe mammalian AP-endonuclease (APE1) repairs abasic (AP) sites and strand breaks with 3' blocks in the genome that are formed both endogenously and as intermediates during base excision repair (BER). APE1 has an unrelated activity as a redox activator (and named Ref-1) for several trans-acting factors. In order to identify whether any of the seven ...

Oxidative stress occurs in cells when the equilibrium between prooxidant and antioxidant species is broken in favor of the prooxidant state. It is due to reactive oxygen species (ROS) generated either by the cellular metabolism such as phagocytosis, mitochondrial respiration, xenobiotic detoxification, or by exogenous factors such as ionizing radiation or chemical compounds performing red-ox ...

Oxidative stress causes DNA mutations which lead to cancer. In the presence of DNA-bound Cu(I), H{sub 2}O{sub 2} is reduced via the metal-catalyzed Fenton reaction to form highly reactive hydroxyl radicals (OH) which can modify the neighboring bases. The frequency of DNA damage at each nucleotide position, modified bases (cleaved by endonuclease III or FormAmidoPYrimidine DNA ...

DNA double-strand breaks (DSBs) are potent sources of genome instability. While there is considerable genetic and molecular information about the disposition of direct DSBs and breaks that arise during replication, relatively little is known about DSBs derived during processing of single-strand lesions, especially for the case of single-strand breaks (SSBs) with 3'-blocked termini generated in ...