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81.
82.
Sidorenko VS Nevinsky GA Zharkov DO 《Biochemical and biophysical research communications》2008,368(1):175-179
Human 8-oxoguanine-DNA glycosylase OGG1 is an enzyme that removes abundant oxidative lesion 8-oxoguanine (8-oxoG) from DNA. Excision of 8-oxoG by OGG1 is inhibited by the abasic DNA reaction product and is stimulated by AP endonuclease APEX1. Besides 8-oxoG, OGG1 shows activity towards several other base lesions. Here we report that APEX1 efficiently stimulates OGG1 on good substrates (8-oxoadenine, 8-oxoinosine, or 6-methoxy-8-oxoguanine opposite to cytosine) but the stimulation is low or absent with poor OGG1 substrates (8-oxoadenine or 8-oxoinosine opposite to thymine; 8-oxoG or 8-aminoguanine opposite to adenine; 8-oxonebularine, 8-metoxyguanine, inosine or guanine opposite to cytosine). APEX1 significantly improves the ability of OGG1 to excise 8-aminoguanine from its naturally occurring pair with cytosine, making it possible that OGG1 repairs this lesion. Overall, APEX1 serves to improve specificity of OGG1 for its biologically relevant substrates. 相似文献
83.
3D analysis of mitosis distribution highlights the longitudinal zonation and diarch symmetry in proliferation activity of the Arabidopsis thaliana root meristem
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Viktoriya V. Lavrekha Taras Pasternak Victor B. Ivanov Klaus Palme Victoria V. Mironova 《The Plant journal : for cell and molecular biology》2017,92(5):834-845
To date CYCB1;1 marker and cortex cell lengths have been conventionally used to determine the proliferation activity of the Arabidopsis root meristem. By creating a 3D map of mitosis distribution we showed that these markers overlooked that stele and endodermis save their potency to divide longer than the cortex and epidermis. Cessation of cell divisions is not a random process, so that mitotic activity within the endodermis and stele shows a diarch pattern. Mitotic activity of all root tissues peaked at the same distance from the quiescent center (QC); however, different tissues stopped dividing at different distances, with cells of the protophloem exiting the cell cycle first and the procambial cells being the last. The robust profile of mitotic activity in the root tip defines the longitudinal zonation in the meristem with the proliferation domain, where all cells are able to divide; and the transition domain, where the cell files cease to divide. 3D analysis of cytokinin deficient and cytokinin signaling mutants showed that their proliferation domain is similar to that of the wild type, but the transition domain is much longer. Our data suggest a strong inhibitory effect of cytokinin on anticlinal cell divisions in the stele. 相似文献
84.
Alvarez-Venegas R Pien S Sadder M Witmer X Grossniklaus U Avramova Z 《Current biology : CB》2003,13(8):627-637
BACKGROUND: The genes of the trithorax (trxG) and Polycomb groups (PcG) are best known for their regulatory functions in Drosophila, where they control homeotic gene expression. Plants and animals are thought to have evolved multicellularity independently. Although homeotic genes control organ identity in both animals and plants, they are unrelated. Despite this fact, several plant homeotic genes are negatively regulated by plant genes similar to the repressors from the animal PcG. However, plant-activating regulators of the trxG have not been characterized. RESULTS: We provide genetic, molecular, functional, and biochemical evidence that an Arabidopsis gene, ATX1, which is similar to the Drosophila trx, regulates floral organ development. The effects are specific: structurally and functionally related flower homeotic genes are under different control. We show that ATX1 is an epigenetic regulator with histone H3K4 methyltransferase activity. This is the first example of this kind of enzyme activity reported in plants, and, in contrast to the Drosophila and the yeast trithorax homologs, ATX1 can methylate in the absence of additional proteins. In its ability to methylate H3K4 as a recombinant protein, ATX1 is similar to the human homolog. CONCLUSIONS: ATX1 functions as an activator of homeotic genes, like Trithorax in animal systems. The histone methylating activity of the ATX1-SET domain argues that the molecular basis of these effects is the ability of ATX1 to modify chromatin structure. Our results suggest a conservation of trxG function between the animal and plant kingdoms despite the different structural nature of their targets. 相似文献
85.
Beneficial effect of taurine depletion on osmotic sodium and calcium loading during chemical hypoxia 总被引:5,自引:0,他引:5
Schaffer SW Solodushko V Kakhniashvili D 《American journal of physiology. Cell physiology》2002,282(5):C1113-C1120
Cellular sodium excess is cytotoxicbecause it increases both the intracellular osmotic load andintracellular calcium concentration ([Ca2+]i). Because sodium levels rise duringhypoxia, it is thought to contribute to hypoxic injury. Thus thepresent study tested the hypothesis that taurine-linked reductions in[Na+]i reduce hypoxia-induced cell injury.Taurine depletion was achieved by exposing isolated neonatalcardiomyocytes to medium containing the taurine analog -Alanine. Aspredicted, the -Alanine-treated cell exhibited less hypoxia-inducednecrosis and apoptosis than the control, as evidenced by lessswelling, shrinkage, TdT-mediated dUTP nick end labeling staining, andaccumulation of trypan blue. After 1 h of chemical hypoxia,[Na+]i was 3.5-fold greater in the controlthan the taurine-deficient cell. Although more taurine was lost fromthe control cell than from the -Alanine-treated cell during hypoxia,the combined taurine and sodium osmotic load was lower in the-Alanine-treated cell. Taurine deficiency also reduced the degree ofhypoxia-induced calcium overload. Thus the observed resistance againsthypoxia-induced necrosis and apoptosis is probably related toan improvement in sodium and calcium handling. 相似文献
86.
Suppression of transgene silencing by matrix attachment regions in maize: a dual role for the maize 5' ADH1 matrix attachment region
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Matrix attachment regions (MARs) are DNA sequences that bind an internal nuclear network of nonhistone proteins called the nuclear matrix. Thus, they may define discrete gene-containing chromatin loops in vivo. We have studied the effects of flanking transgenes with MARs on transgene expression levels in maize callus and in transformed maize plants. Three MAR elements, two from maize (Adh1 5' MAR and Mha1 5' MAR) and one from yeast (ARS1), had very different effects on transgene expression that bore no relation to their affinity for the nuclear matrix in vitro. In callus, two of the MAR elements (Adh1 5' MAR and ARS1) reduced transgene silencing but had no effect on the variability of expression. In transgenic plants, Adh1 5' MAR had the effect of localizing beta-glucuronidase expression to lateral root initiation sites. A possible model accounting for the function of Adh1 5' MAR is discussed. 相似文献
87.
88.
Saleh A Al-Abdallat A Ndamukong I Alvarez-Venegas R Avramova Z 《Nucleic acids research》2007,35(18):6290-6296
Tightly balanced antagonism between the Polycomb group (PcG) and the Trithorax group (TrxG) complexes maintain Hox expression patterns in Drosophila and murine model systems. Factors belonging to the PcG/TrxG complexes control various processes in plants as well but whether they participate in mechanisms that antagonize, balance or maintain each other's effects at a particular gene locus is unknown. CURLY LEAF (CLF), an Arabidopsis homolog of enhancer of zeste (EZ) and the ARABIDOPSIS HOMOLOG OF TRITHORAX (ATX1) control the expression of the flower homeotic gene AGAMOUS (AG). Disrupted ATX1 or CLF function results in misexpression of AG, recognizable phenotypes and loss of H3K4me3 or H3K27me3 histone H3-tail marks, respectively. A novel idea suggested by our results here, is that PcG and TrxG complexes function as a specific pair generating bivalent chromatin marks at the silent AG locus. Simultaneous loss of ATX1 and CLF restored AG repression and normalized leaf phenotypes. At the molecular level, disrupted ATX1 and CLF functions did not lead to erasure of the CLF- and ATX1-generated epigenetic marks, as expected: instead, in the double mutants, H3K27me3 and H3K4me3 tags were partially restored. We demonstrate that ATX1 and CLF physically interact linking mechanistically the observed effects. 相似文献
89.
Viktoriya Syrovatkina Xin‐Yun Huang 《Protein science : a publication of the Protein Society》2019,28(2):305-312
Heterotrimeric G‐proteins are cellular signal transducers. They mainly relay signals from G‐protein‐coupled receptors (GPCRs). GPCRs function as guanine nucleotide‐exchange factors to active these G‐proteins. Based on the sequence and functional similarities, these G‐proteins are grouped into four subfamilies: Gs, Gi, Gq, and G12/13. The G12/13 subfamily consists of two members: G12 and G13. G12/13‐mediated signaling pathways play pivotal roles in a variety of physiological processes, while aberrant regulation of this pathway has been identified in various human diseases. Here we summarize the signaling mechanisms and physiological functions of Gα13 in blood vessel formation and bone homeostasis. We further discuss the expanding roles of Gα13 in cancers, serving as oncogenes as well as tumor suppressors. 相似文献
90.
Zarko Grozdanovic Luis C. Berrocal Almanza Surabhi Goyal Abid Hussain Tilman E. Klassert Dominik Driesch Viktoriya Tokaryeva Yvonne Yi-Na L?schmann Gadamm Sumanlatha Niyaz Ahmed Vijayalakshmi Valluri Ralf R. Schumann Birgit Lala Hortense Slevogt 《PloS one》2015,10(9)