Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: 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 effects of oxygen and misonidazole on the induction of DNA lesions were examined in human TK6 lymphoblasts irradiated with 60Co gamma rays. We have investigated both the formation and subsequent repair of two classes of DNA damage, single-strand breaks and lesions recognized by the gamma endonuclease activity in a cell-free extract of Micrococcus luteus. Relative to irradiation under hypoxia, single-strand break yields were increased by the presence of either oxygen or misonidazole at the time of irradiation. In contrast, M. luteus enzyme-sensitive site yields were unaffected by the presence of either oxygen or misonidazole. No significant differences in single-strand break or enzyme-sensitive site repair kinetics were observed for lesions induced under any of the irradiation conditions employed. These results confirm the sensitizing effects of oxygen and oxygen-mimetic drugs on the induction of single-strand breaks but provide no support for their ability to enhance the induction of enzyme-sensitive sites.
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PMID:Induction and repair of DNA damage in gamma-irradiated human lymphoblasts: irradiation in the presence and absence of misonidazole. 326 83

Genomic DNAs from twelve Japanese patients with steroid 21-hydroxylase [21-OHase; steroid 21-monooxygenase; steroid, hydrogen-donor:oxygen oxidoreductase (21-hydroxylating); EC 1.14.99.10] deficiency were analyzed by Southern blot hybridization. A 3.7-kilobase (kb) Taq I and a 1.7-kb Pvu II restriction endonuclease fragment that correspond to a 21-OHase B gene were absent from the DNA of two unrelated patients with the salt-wasting form of the disease. However, a 10.5-kb Bgl II fragment corresponding to the region encompassing the 21-OHase B gene was still present in these two patients. The genes encoding 21-OHase were cloned from one of these two patients, who was homozygous by descent for HLA-A26;B39;C4A3;C4B1;DR4. Restriction endonuclease mapping as well as partial nucleotide sequencing analysis revealed that the 21-OHase B gene of the patient has been converted to the pseudogene, 21-OHase A, as far as the critical 0.5-kb sequence was concerned. Thus, the defect was due to both chromosomes each carrying two copies of 21-OHase A pseudogene and lacking functional 21-OHase B gene.
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PMID:Gene conversion-like events cause steroid 21-hydroxylase deficiency in congenital adrenal hyperplasia. 350 Apr 73

The restriction endonuclease EcoRI hydrolyzes the Rp diastereomer of d(pGGsAATTCC), an analogue of d(pGGAATTCC) containing a chiral phosphorothioate group at the cleavage site between the deoxyguanosine and the deoxyadenosine residues (Connolly, B.A., Potter, B.V.L., Eckstein, F., Pingoud, A., and Grotjahn, L. (1984) Biochemistry 23, 3343-3453). Performing the reaction in H2(18)O leads to d(pGG) and the hexanucleotide d([18O, S]pAATTCC) which has an 18O-containing phosphorothioate group at the 5' terminus. Further hydrolysis of this hexamer with nuclease P1 yields deoxyadenosine 5'-O-[18O]phosphorothioate which can be stereospecifically phosphorylated with adenylate kinase and pyruvate kinase to give Sp-[18O] deoxyadenosine 5'-O-(1-thiotriphosphate). 31P NMR spectroscopy shows the oxygen-18 in this compound to be in a bridging position between the alpha- and beta-phosphorus atoms. Thus, the hydrolysis reaction catalyzed by EcoRI proceeds with inversion of configuration at phosphorus. This result is compatible with a direct enzyme-catalyzed nucleophilic attack of H2O at phosphorus without involvement of a covalent enzyme intermediate.
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PMID:The stereochemical course of the restriction endonuclease EcoRI-catalyzed reaction. 608 16

The effect of oxygen tension on the transcription of genes coding for the photosynthetic apparatus of Rhodopseudomonas capsulata was determined by the Southern hybridization technique. Restriction endonuclease digests of the R-prime plasmid pRPS404 and a subcloned fragment thereof served as DNA probes for genetically defined regions. The results showed that transcripts corresponding to the genes for certain pigment-binding polypeptides increase in amount by about 40-fold after a drop in oxygen tension. Transcripts hybridizing to genes involved in bacteriochlorophyll biosynthesis increase to a much lesser extent, and several genes involved in carotenoid biosynthesis are not affected by pO2.
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PMID:Variation of levels of mRNA coding for antenna and reaction center polypeptides in Rhodopseudomonas capsulata in response to changes in oxygen concentration. 619 43

Microcytic red cells from a 70 year old Negro man with mild anemia contained only hemoglobin G-Philadelphia. Red cells from all of his children had low-normal MCV's, and contained 32-34 percent of the abnormal hemoglobin. Oxygen affinity of his blood and stability of his hemolysate were normal, suggesting that his mild anemia was not caused by the the abnormal hemoglobin. Restriction endonuclease analyses of DNA from the proband and his offspring showed that the alpha G-Philadelphia globin gene exists in only one copy per chromosome. The new gene was probably created by an unequal cross-over which deleted an alpha globin coding sequence (derived from one or both alpha globin genes), as well as some or all of the DNA sequence between those genes.
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PMID:Homozygous alpha thalassemia/Hb G Philadelphia. 629 2

The presence of the alpha-globin frameshift mutant, Hb Wayne, in three generations of a second family is described. The data include a hematological evaluation of the four heterozygotes, structural characterization of the variant, the use of HPLC for the separation of tryptic and chymotryptic peptides, functional analyses of the isolated variant showing high affinity for oxygen and the (near) absence of a Bohr effect, and alpha chain gene organization analyses with restriction endonuclease technology suggesting that the Hb Wayne heterozygote has a full complement of four alpha globin genes.
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PMID:Hb Wayne, the frameshift variant with extended alpha chains observed in a Caucasian family from Alabama. 632 75

In Physarum polycephalum, microplasmodia differentiated into spherules when cultures were aged for 8-10 days. Respiration rates of the microplasmodia decreased rapidly with ageing to a 90% decrease in oxygen consumption over 9 days. We studied this phenomena by isolating and characterizing mitochondria from microplasmodia and spherules at different stages of spherulation. Oxygen uptake by the isolated mitochondria decreased with spherulation. Morphological and biochemical analyses showed that mitochondrial differentiation to inactive state was characterized by a decrease not only in dimension but also of content (DNA, RNA and protein). Diminutive mitochondria contained small particle-shaped mitochondrial nuclei. The DNA content, measured by microscopic fluorometry, was about 1.15 and 0.58 X 10(-10) g, which corresponded to about 16 and 8 genome copies, respectively (e.g., 32 genome copies per mitochondrion at mitochondrial G1). Restriction endonuclease analysis showed that the physical structure and methylation pattern of the mtDNA had not changed although the DNA content per mitochondrion had decreased remarkably with spherulation. This showed that changes in the ploidy level of the mitochondrial nucleus during spherulation were due to reduction in the number of whole mitochondrial genomes.
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PMID:Variance of ploidy in mitochondrial nucleus during spherulation in Physarum polycephalum. 664 7

Despite vigorous research, there is yet no agreement on the biochemical mechanisms responsible for the loss of replicative potential of diploid cultured cells. In contrast to the program theories of in vitro cell aging, we propose that, as already suggested by Minot in 1907, senescence is the result of cell differentiation. We further maintain that the fundamental cause of cell aging is an instability of the mitochondrial genome because of a lack of balance between mitochondrial repair and the disorganizing effects of oxygen radicals which arise in the respiring mitochondria of terminally differentiated cells. This probably results in intrinsic mitochondrial mutagenesis which may be followed by endonuclease degradation of the altered mitochondrial DNA. Since the mitochondrial genome controls the synthesis of several hydrophobic proteins of the inner mitochondrial membrane, the postulated denaturation or loss of mtDNA will prevent the replication of the organelles. Thus, deprived of the ability to regenerate their mitochondrial populations, the cells will sustain an irreversible decline in their ability to synthesize ATP, with concomitant senescent degradation of physiological performance and eventual death.
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PMID:A two-step hypothesis on the mechanisms of in vitro cell aging: cell differentiation followed by intrinsic mitochondrial mutagenesis. 672 17

Isolated mitochondria of faba beans carrying two different determinisms of the cytoplasmic male sterility (cytoplasms 447 and 350) have been compared to fertile lines. 1. In addition to the major mitochondrial DNA, five small DNA species (in the range of 1000-2000 base pairs) were detected by agarose gel electrophoresis in the four cytoplasms. An additional small DNA species was found specifically in the cytoplasm 350. After endonuclease restriction of the mitochondrial DNA, the patterns obtained for both male-sterile cytoplasms were identical to each other but distinct by two to four fragments from the patterns obtained for male-fertile cytoplasms. 2. [35S]Methionine labeling in situ of the mitochondrial protein synthesis revealed an additional polypeptide (Mr = 25000) detected only in the two male-sterile cytoplasms. 3. The male-sterile cytoplasm 350 showed a decrease of the respiratory state 3 of oxygen uptake during oxidation of NADH or malate + pyruvate. This decrease is thought to reflect a smaller capacity of the respiratory chain. These specific mitochondrial modifications support the hypothesis of a mitochondrial localization of the cytoplasmic male sterility determinant in faba beans.
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PMID:Mitochondrial modifications associated with the cytoplasmic male sterility in faba beans. 689 Apr 54

In this investigation, normal and Fanconi's anemia fibroblasts were exposed to high concentrations of oxygen and the effects of this treatment on DNA were analyzed by alkaline elution. No DNA single-strand breaks were detected in either cell type with up to 20 h incubation in high(50-95%) concentrations of O2. No evidence of DNA damage by O2 could be detected with an endonuclease preparation from Micrococcus luteus. Cells which have been treated with various DNA-damaging agents in the presence of the polymerase inhibitor cytosine arabinoside have been shown to accumulate DNA single-strand breaks during DNA excision repair. When cells were treated with the polymerase inhibitor in 50 or 95% O2, a low level of DNA single-strand breaks accumulated in both cells types. However, no significant differences in the frequency of DNA single-strand breaks were detected between normal and Fanconi's anemia cells after exposure to high O2.
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PMID:Normal response of fanconi's anemia cells to high concentrations of O2 as determined by alkaline elution. 713 67


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