Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:3.2.1.31 (beta-glucuronidase)
 7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

DNA damage occurs as a by-product of intrinsic cellular processes, like DNA replication, or as a consequence of exposure to genotoxic agents. Organisms have evolved multiple mechanisms to avoid, tolerate, or repair DNA lesions. To gain insight into these processes, we have isolated mutants hypersensitive to DNA-damaging agents in the green alga Chlamydomonas reinhardtii. One mutant, Ble-1, showed decreased survival when it was treated with methyl methanesulfonate (MMS), bleomycin, or hydrogen peroxide (H2O2) but behaved like the wild type when it was exposed to UVC irradiation. Ble-1 carries an extensive chromosomal deletion that includes the gene encoding cytosolic thioredoxin h1 (Trxh1). Transformation of Ble-1 with a wild-type copy of Trxh1 fully corrected the MMS hypersensitivity and partly restored the tolerance to bleomycin. Trxh1 also complemented a defect in the repair of MMS-induced DNA strand breaks and alkali-labile sites. In addition, a Trxh1-beta-glucuronidase fusion protein translocated to the nucleus in response to treatment with MMS. However, somewhat surprisingly, Trxh1 failed to correct the Ble-1 hypersensitivity to H2O2. Moreover, Trxh1 suppression by RNA interference in a wild-type strain resulted in enhanced sensitivity to MMS and DNA repair defects but no increased cytotoxicity to H2O2. Thioredoxins have been implicated in oxidative-stress responses in many organisms. Yet our results indicate a specific role of Chlamydomonas Trxh1 in the repair of MMS-induced DNA damage, whereas it is dispensable for the response to H2O2. These observations also suggest functional specialization among cytosolic thioredoxins since another Chlamydomonas isoform (Trxh2) does not compensate for the lack of Trxh1.
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PMID:Functional specialization of Chlamydomonas reinhardtii cytosolic thioredoxin h1 in the response to alkylation-induced DNA damage. 1570 88

Oxygen free radicals are thought to play an essential role in senescence, especially those derived from peroxisomes. Therefore, the activities of different isoforms of the peroxisomal hydrogen peroxide (H2O2)-scavenging enzyme catalase (CAT) were analysed during senescence of Arabidopsis. CAT2 activity decreased with bolting time parallel with cytosolic ascorbate peroxidase 1 (APX1) activity before loss of chlorophyll could be measured. At the same time point, the H2O2 content increased. Subsequently, the stress-inducible CAT3 isoform was activated and APX1 activity was recovered, accompanied by a decline of the H2O2 content. In very late stages, low activities of the seed-specific CAT1 became detectable in leaves, but H2O2 increased again. Further analyses of CAT expression by promoter: beta-glucuronidase (GUS) fusions in transgenic plants revealed a vasculature-specific CAT3 expression, whereas CAT2 expression turned out to be specific for photosynthetic active tissues. CAT2 expression is down-regulated during leaf senescence, while CAT3 expression is induced with age and corresponds to an accumulation of H2O2 in the vascular bundles. CAT2 down-regulation on the transcriptional level appears as the initial step in creating the H2O2 peak during bolting time, while the decrease in APX1 activity might only be a secondary and amplifying effect.
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PMID:Senescence-specific regulation of catalases in Arabidopsis thaliana (L.) Heynh. 1708 Sep 32

cgMT1 is a metallothionein (MT)-like gene that was isolated from a cDNA library of young nitrogen-fixing nodules resulting from the symbiotic interaction between Frankia spp. and the actinorhizal tree Casuarina glauca. cgMT1 is highly transcribed in the lateral roots and nitrogen-fixing cells of actinorhizal nodules; it encodes a class I type 1 MT. To obtain insight into the function of cgMT1, we studied factors regulating the expression of the MT promoter region (PcgMT1) using a beta-glucuronidase (gus) fusion approach in transgenic plants of Arabidopsis thaliana. We found that copper, zinc, and cadmium ions had no significant effect on the regulation of PcgMT1-gus expression whereas wounding and H2O2 treatments led to an increase in reporter gene activity in transgenic leaves. Strong PcgMT1-gus expression also was observed when transgenic plants were inoculated with a virulent strain of the bacterial pathogen Xanthomonas campestris pv. campestris. Transgenic Arabidopsis plants expressing cgMT1 under the control of the constitutive 35S promoter were characterized by reduced accumulation of H2O2 when leaves were wounded and by increased susceptibility to the bacterial pathogen X. campestris. These results suggest that cgMT1 could play a role during the oxidative response linked to biotic and abiotic stresses.
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PMID:Functional analysis of the metallothionein gene cgMT1 isolated from the actinorhizal tree Casuarina glauca. 1791 25

Hydrogen peroxide (H(2)O(2)) is discussed as being a signaling molecule in Arabidopsis (Arabidopsis thaliana) leaf senescence. Intracellular H(2)O(2) levels are controlled by the H(2)O(2)-scavenging enzyme catalase in concert with other scavenging and producing systems. Catalases are encoded by a small gene family, and the expression of all three Arabidopsis catalase genes is regulated in a senescence-associated manner. CATALASE2 (CAT2) expression is down-regulated during bolting time at the onset of leaf senescence and appears to be involved in the elevation of the H(2)O(2) level at this time point. To understand the role of CAT2 in senescence regulation in more detail, we used CAT2 promoter fragments in a yeast one-hybrid screen to isolate upstream regulatory factors. Among others, we could identify G-Box Binding Factor1 (GBF1) as a DNA-binding protein of the CAT2 promoter. Transient overexpression of GBF1 together with a CAT2:beta-glucuronidase construct in tobacco (Nicotiana benthamiana) plants and Arabidopsis protoplasts revealed a negative effect of GBF1 on CAT2 expression. In gbf1 mutant plants, the CAT2 decrease in expression and activity at bolting time and the increase in H(2)O(2) could no longer be observed. Consequently, the onset of leaf senescence and the expression of senescence-associated genes were delayed in gbf1 plants, clearly indicating a regulatory function of GBF1 in leaf senescence, most likely via regulation of the intracellular H(2)O(2) content.
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PMID:G-Box binding factor1 reduces CATALASE2 expression and regulates the onset of leaf senescence in Arabidopsis. 2835 46

The active compounds in the roots of Scutellaria baicalensis Georgi, a traditional Chinese medicinal plant, are mainly flavonoids which have anti-inflammatory, antitumour, and anti-HIV activity, respectively. The increasing annual average temperature has rendered the S. baicalensis plants grown in some ancient producing regions no longer suitable for their medicinal usage. Hydrogen peroxide plays an important role in root responses to abnormal temperature in S. baicalensis. Baicalin and baicalein and antioxidative enzymes were anticipated to detoxify H2O2 in S. baicalensis. Here, we show that abnormal temperatures (10 and 40 degrees C) decreased the content of flavonoids as compared with the normal temperature (30 degrees C), and the transcripts of UDP-glucuronate:baicalein 7-O-glucuronosyltransferase and beta-glucuronidase involved in the interconversion between baicalin and baicalein were affected by the 40-degrees C treatment. High temperature also increased the activities of catalase and peroxidase. Reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that the transcript levels of peroxidase 2, peroxidase 3, monodehydroascorbate reductase 2, and dehydroascorbate reductase were significantly increased under high-temperature conditions. The respective genes would be candidates for improvement of the adaptation of S. baicalensis plants to abnormal temperatures and for regulation of the contents of the active compounds.
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PMID:Flavonoids and antioxidative enzymes in temperature-challenged roots of Scutellaria baicalensis Georgi. 2248 44


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