共查询到20条相似文献，搜索用时 31 毫秒
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Mailand N Falck J Lukas C Syljuâsen RG Welcker M Bartek J Lukas J 《Science (New York, N.Y.)》2000,288(5470):1425-1429
To protect genome integrity and ensure survival, eukaryotic cells exposed to genotoxic stress cease proliferating to provide time for DNA repair. Human cells responded to ultraviolet light or ionizing radiation by rapid, ubiquitin- and proteasome-dependent protein degradation of Cdc25A, a phosphatase that is required for progression from G1 to S phase of the cell cycle. This response involved activated Chk1 protein kinase but not the p53 pathway, and the persisting inhibitory tyrosine phosphorylation of Cdk2 blocked entry into S phase and DNA replication. Overexpression of Cdc25A bypassed this mechanism, leading to enhanced DNA damage and decreased cell survival. These results identify specific degradation of Cdc25A as part of the DNA damage checkpoint mechanism and suggest how Cdc25A overexpression in human cancers might contribute to tumorigenesis. 相似文献
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The yeast cell cycle gene CDC34 encodes a ubiquitin-conjugating enzyme 总被引：58，自引：0，他引：58
M G Goebl J Yochem S Jentsch J P McGrath A Varshavsky B Byers 《Science (New York, N.Y.)》1988,241(4871):1331-1335
Mutants in the gene CDC34 of the yeast Saccharomyces cerevisiae are defective in the transition from G1 to the S phase of the cell cycle. This gene was cloned and shown to encode a 295-residue protein that has substantial sequence similarity to the product of the yeast RAD6 gene. The RAD6 gene is required for a variety of cellular functions including DNA repair and was recently shown to encode a ubiquitin-conjugating enzyme. When produced in Escherichia coli, the CDC34 gene product catalyzed the covalent attachment of ubiquitin to histones H2A and H2B in vitro, demonstrating that the CDC34 protein is another distinct member of the family of ubiquitin-conjugating enzymes. The cell cycle function of CDC34 is thus likely to be mediated by the ubiquitin-conjugating activity of its product. 相似文献
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W K Sinclair 《Science (New York, N.Y.)》1968,159(813):442-444
Cysteamine present during x-irradiation protects synchronized Chinese hamster cells in culture against lethal damage at all stages of the cell cycle. The effect is greatest for cells irradiated at sensitive stages such as G(1) and least for resistant cells; for example, late S (dose-modifying factors 4.2 and 2.7, respectively). The effect of 50 millimolar cysteamine is to render almost invariant the normally variant x-ray age response for lethality. This suggests that there are two components of x-ray damage, only one of which is age dependent, and it is against this component that cysteamine protects the cell. Cystamine, however, has no protective effect upon these cells at any stage of the cell cycle. 相似文献
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Cd胁迫诱导拟南芥幼苗DNA损伤分析 总被引：1，自引：0，他引：1
以拟南芥为供试植物,通过基于随机引物扩增多态性(RAPD)法的DNA损伤分析,酶联免疫吸附(ELISA)法的DNA甲基化分析以及Real-time PCR的DNA损伤修复与细胞周期相关基因的表达分析,研究了Cd(0、0.125、0.25、1.0、2.5 mg·L~(-1))胁迫5 d的拟南芥幼苗DNA损伤、DNA损伤修复系统以及细胞周期对胁迫的响应。结果显示,随Cd浓度的增加DNA损伤加剧,全基因组甲基化水平较对照组显著增加(P0.01或P0.05),细胞周期调控基因PCNA1、PCNA2,错配修复(MMR)基因MLH1、MSH_2、MSH6,非同源末端连接(NHEJ)标志基因KU70、MRE11、GR1,同源重组(HR)标志基因RAD51、BRCA1的表达均与Cd胁迫浓度呈明显的倒U型剂量效应关系,DNA修复系统对Cd胁迫的敏感性依次为MMRHRNHEJ。该结果表明:轻度Cd胁迫主要引起DNA错配损伤,并且该损伤易修复;随着Cd胁迫的增强,会引起DNA断裂与染色体损伤,损伤较难修复。另外,对Cd胁迫响应最敏感的MSH6、MLH1基因可作为表征Cd胁迫对于拟南芥遗传毒性效应的有效生物标记物。 相似文献
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When prototrophic yeast cells are cultured under nutrient-limited conditions that mimic growth in the wild, rather than in the high-glucose solutions used in most laboratory studies, they exhibit a robustly periodic metabolic cycle. Over a cycle of 4 to 5 hours, yeast cells rhythmically alternate between glycolysis and respiration. The cell division cycle is tightly constrained to the reductive phase of this yeast metabolic cycle, with DNA replication taking place only during the glycolytic phase. We show that cell cycle mutants impeded in metabolic cycle-directed restriction of cell division exhibit substantial increases in spontaneous mutation rate. In addition, disruption of the gene encoding a DNA checkpoint kinase that couples the cell division cycle to the circadian cycle abolishes synchrony of the metabolic and cell cycles. Thus, circadian, metabolic, and cell division cycles may be coordinated similarly as an evolutionarily conserved means of preserving genome integrity. 相似文献
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Checkpoints are evolutionarily conserved signaling mechanisms that arrest cell division and alter cellular stress resistance in response to DNA damage or stalled replication forks. To study the consequences of loss of checkpoint functions in whole animals, checkpoint genes were inactivated in the nematode C. elegans. We show that checkpoint proteins are not only essential for normal development but also determine adult somatic maintenance. Checkpoint proteins play a role in the survival of postmitotic adult cells. 相似文献
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G1 events and regulation of cell proliferation 总被引：212，自引：0，他引：212
A B Pardee 《Science (New York, N.Y.)》1989,246(4930):603-608
Cells prepare for S phase during the G1 phase of the cell cycle. Cell biological methods have provided knowledge of cycle kinetics and of substages of G1 that are determined by extracellular signals. Through the use of biochemical and molecular biological techniques to study effects of growth factors, oncogenes, and inhibitors, intracellular events during G1 that lead to DNA synthesis are rapidly being discovered. Many cells in vivo are in a quiescent state (G0), with unduplicated DNA. Cells can be activated to reenter the cycle during G1. Similarly, cells in culture can be shifted between G0 and G1. These switches in and out of G1 are the main determinants of post-embryonic cell proliferation rate and are defectively controlled in cancer cells. 相似文献
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53BP1, a mediator of the DNA damage checkpoint 总被引：2，自引：0，他引：2
53BP1 binds to the tumor suppressor protein p53 and has a potential role in DNA damage responses. We used small interfering RNA (siRNA) directed against 53BP1 in mammalian cells to demonstrate that 53BP1 is a key transducer of the DNA damage checkpoint signal. 53BP1 was required for p53 accumulation, G2-M checkpoint arrest, and the intra-S-phase checkpoint in response to ionizing radiation. 53BP1 played a partially redundant role in phosphorylation of the downstream checkpoint effector proteins Brca1 and Chk2 but was required for the formation of Brca1 foci in a hierarchical branched pathway for the recruitment of repair and signaling proteins to sites of DNA damage. 相似文献
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【目的】试验以草地贪夜蛾细胞sf9作为受体，检测氯化汞对其生长发育的影响。【方法】采用台盼兰染料排斥法测定细胞活力，苏木素-伊红染色法检测细胞中的微核，对经氯化汞处理诱变的病毒AcMNPV 的DNA进行PCR扩增，产物经测序后进行分子突变分析。【结果】sf9细胞在4 ?g·ml-1的氯化汞浓度作用下，其细胞表面变得粗糙，分裂生长减慢，当剂量增大到7 ?g·ml-1时，便可观察到一些细胞的细胞膜破裂，在9 ?g·ml-1时，某些细胞的完整性受到破坏。用苏木素-伊红染色法检测细胞中的微核现象时，9 ?g·ml-1氯化汞处理区的微核率高达6.8%，有些细胞出现三核甚至多核的核裂现象，反映部分细胞的完整性受到一定程度的损伤。AcMNPV病毒经氯化汞短时间处理后接种于sf9细胞，多角体在sf9细胞中的形成数目较对照区少，异常多角体的比例增加，抽提经氯化汞处理的AcMNPV 的DNA，采取PCR技术进行扩增反应，对获得的扩增产物进行测序分析，发现DNA序列上的碱基有2处G→C、T→C的转换和碱基缺失的现象。【结论】一定剂量的氯化汞将会引起草地贪夜蛾sf9细胞及核型多角体病毒的损伤与致突变。 相似文献
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马尾松树皮提取物体外抑制人大肠癌细胞生长机理初探 总被引：1，自引：0，他引：1
为探讨马尾松树皮提取物(PMBE)体外抑制大肠癌LoVo细胞生长的作用特点和机理,通过MTT、显微镜术、凝胶电泳和流式细胞术,研究PMBE抑制LoVo细胞生长的特点,运用免疫组化和RT-PCR探究相关分子机理。结果表明:PMBE时间-剂量依赖地抑制LoVo细胞的体外生长;PMBE处理后,流式细胞检测发现LoVo细胞周期阻滞于G1或S期,同时可检测到亚二倍体峰的出现;荧光镜检和透射电镜观察可看到LoVo细胞的核皱缩、边集甚或碎裂,以及有凋亡小体形成,其基因组经过凝胶电泳呈现典型的梯形Ladder;RT-PCR和免疫组化结果显示PMBE处理可上调LoVo细胞中p53和p21基因的转录效率,并下调Bcl-2的蛋白表达量。说明PMBE通过上调p53和p21的表达量阻滞细胞周期、下调Bcl-2的表达量诱导细胞凋亡的双重机制,抑制LoVo细胞的体外生长,可供进一步探索相关信号传导通路参考。 相似文献
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Inhibition with either 5-fluorodeoxyuridine or deoxyadenosine for specified periods during the division cycle of the HeLa S3 cell shows that the mid-interphase peak in sensitivity occurs just before DNA replication begins. Sensitivity subsequently decreases only after synthesis of DNA is resumed. One interpretation of the relation between fluctuations in sensitivity and in DNA synthesis is that the lethal radiation damage to these cells occurs in DNA. 相似文献
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【目的】研究α-三联噻吩（α-T）对斜纹夜蛾（Spodoptera litura）SL细胞线粒体膜电位及细胞周期的影响。【方法】通过Rhodamine123染色和流式细胞术（flow cytometry,FCM）研究α-T处理SL细胞24 h和48 h后细胞线粒体膜电位的变化,并通过PI染色和FCM,测定α-T处理SL细胞24 h和48 h后细胞周期各时相百分率的变化。【结果】光活化后的α-T处理SL细胞24 h后,0.0625 μg•mL-1浓度和0.1250 μg•mL-1浓度处理组细胞线粒体膜电位的变化幅度不大,而0.5000 μg•mL-1浓度处理组细胞线粒体膜电位明显升高,48 h后高浓度处理组（1.0000 μg•mL-1）导致线粒体膜电位明显去极化;处理24 h后,低浓度（0.0625 μg•mL-1）处理组细胞被阻滞于S期,而高于此浓度的光照处理组细胞被阻滞于G2/M期,48 h后,浓度≤0.1250 μg•mL-1的光照处理细胞被阻滞于G2/M期,而浓度＞0.1250 μg•mL-1的光照处理组细胞被阻滞于S期。【结论】SL细胞经α-T处理后,细胞处于一系列复杂的动态变化中。当细胞本身不能扭转ROS造成的氧化损伤时,细胞线粒体膜电位和细胞周期时相即出现较大幅度的变化,这种变化决定着细胞的受损程度和细胞的死亡途径。 相似文献
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Hydroxyurea: differential lethal effects on cultured mammalian cells during the cell cycle 总被引：19，自引：0，他引：19
W K Sinclair 《Science (New York, N.Y.)》1965,150(704):1729-1731
Hydroxyurea has a differential lethal effect on cultured Chinesehamster cells that are at different stages in their cell cycle. Cells synthesizing DNA at the time of exposure to the drug are lethally damaged. Cells in the phase of growth preceding DNA synthesis (G(1)) survive but are prevented from beginning DNA synthesis. Cells in the phase after DNA synthesis (G(2)) survive and appear to progress until just before the beginning of the next period of DNA synthesis. This differential lethal and inhibitory effect of hydroxyurea may be useful for synchronizing asynchronous cell populations and explaining effects of the drug in human therapy. 相似文献
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I G Walker 《Science (New York, N.Y.)》1966,151(706):99-101
After exposure to 5-fluorodeoxyuridine, L-cells are considerably more sensitive to the lethal effect of sulfur mustard than after they have been released from this block by addition of thymidine and allowed to proceed into the G2 phase of the division cycle. Nevertheless, for both populations, the amounts of mustard bound per cell and per nucleus (expressed as the amount of mustard per unit of protein) were the same. Likewise, the amounts of mustard bound per unit of DNA were the same for both populations. 相似文献
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Nougayrède JP Homburg S Taieb F Boury M Brzuszkiewicz E Gottschalk G Buchrieser C Hacker J Dobrindt U Oswald E 《Science (New York, N.Y.)》2006,313(5788):848-851
Transient infection of eukaryotic cells with commensal and extraintestinal pathogenic Escherichia coli of phylogenetic group B2 blocks mitosis and induces megalocytosis. This trait is linked to a widely spread genomic island that encodes giant modular nonribosomal peptide and polyketide synthases. Contact with E. coli expressing this gene cluster causes DNA double-strand breaks and activation of the DNA damage checkpoint pathway, leading to cell cycle arrest and eventually to cell death. Discovery of hybrid peptide-polyketide genotoxins in E. coli will change our view on pathogenesis and commensalism and open new biotechnological applications. 相似文献
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An origin unwinding activity regulates initiation of DNA replication during mammalian cell cycle 总被引：26，自引：0，他引：26
An in vitro assay was developed to study the positive factors that regulate the onset of DNA replication during the mammalian cell cycle. Extracts prepared from cells at defined positions in the cell cycle were used to examine the replication of SV40 DNA in a cell free system. Extracts prepared from S phase cells were ten times more efficient at initiating replication at the SV40 origin than were extracts from G1 cells, whereas elongation rates were similar in G1 and S reactions. At a discrete point in the cell cycle, just before the cell's entry into S, an activity appeared that was required, in conjunction with SV40 T antigen, for site specific initiation at the SV40 origin. This factor had a role in unwinding DNA at the replication origin. 相似文献