Silencing ATM gene gave rise to enhanced apoptotic response to irradiation and i rradiation like chemotherapy agents, this paper explored the crucial identities of the molecular elements responsible for the enhanced...Silencing ATM gene gave rise to enhanced apoptotic response to irradiation and i rradiation like chemotherapy agents, this paper explored the crucial identities of the molecular elements responsible for the enhanced apoptotic response in U937 cells mediated by silencing ATM gene. Two U937 cell mutants named U937 ASPI3K (ATM, negative) and U937 pZeosv2(+) (ATM, wild type) were used as a cell model system to identify the critical molecule(s) responsible for the varied apoptotic response in the absence or presence of ATM gene. Apoptosis was examined by measuring concentrations of free nucleosome in U937 cells. Western blot was employed to measure nuclear protein abundance of CDC25A, CDC25B, CDC25C, total p34cdc2, p34cdc2 (Thr 161) or p34cdc2 (Thr 14,Tyr 15). RT PCR was used to estimate CDC25 transcript levels. U937 ASPI3K exhibited an enhanced apoptotic response to lower dosage of irradiation, which could not be blocked by protein synthesis inhibitor. Protein serine threonine phosphatase inhibitor or cyclin dependent kinase (CDK) inhibitors, on the other hand, abolished the enhancement indicated that protein phosphorylation/dephosphorylation modification and CDK activity are required for the enhanced apoptotic response in the absence of ATM gene. Upon irradiation, p34cdc2 in U937 pZeosv2 (+) was maintained in an inactive state by phosphorylation on threonine 14 (Thr 14) and tyrosine 15 (Tyr 15), which was associated with a dramatic decrease of nuclear CDC25A, CDC25B and CDC25C proteins. In contrast, p34cdc2 in U937 ASPI3K maintained in an active state by dephosphorylation on threonine 14 (Thr 14) and tyrosine 15 (Tyr 15), which was associated with constant nuclear CDC25A, CDC25B and CDC25C protein abundance before and after irradiation. The responsive decrease of nuclear CDC25 proteins occurred at the post transcription level. Silencing ATM gene blocks the responsive decrease of nuclear CDC25 proteins, which is responsible for failure to inactivate p34cdc2 after irradiation. Active p34cdc2 and CDK2, in turn, acts as the death executors to trigger apoptosis. In abstract, aberrantly activated CDK activity is the critical molecular mechanism central to enhanced apoptotic responses in the absence of ATM gene.展开更多
Objective： To learn the effect of allitridi on inducing mitotic arrest in human gastric cell line SGC-7901 and its possible mechanisms. Methods： We treated SGC-7901 cells with allitridi, and observed the proliferati...Objective： To learn the effect of allitridi on inducing mitotic arrest in human gastric cell line SGC-7901 and its possible mechanisms. Methods： We treated SGC-7901 cells with allitridi, and observed the proliferation inhibitory rate with MTT colometric assay, changes of cell cycle using flow cytometry and Switzerland-Giemsa＇s staining, and morphologic changes of the microtubule structure and location changes of cyclin BI expression using immunofluorescence and confocal laser scanning microscope. Furthermore, the expression of cyclin B1 was analyzed quantitatively using Leica confocal software. Results： SGC-7901 cells were inhibited after exposure to allitridi and the IC50 was 7.2μg/ml for 24 h, 20μg/ml for 72 h. When the cells were treated with allitridi at concentrations of 3, 6, and 9μg/ml for 24 h respectively, there was a declining tendency in the percentage of G0/G1 cell but an increasing tendency in GE/M cell in the allitridi treated group compared with that of control （P〈0.01）. When cells were treated allitridi at concentration of 6 μg/ml for 24 h, its mitotic index was much higher （P〈0.01） than that of control, suggesting that allitridi caused arrest of gastric cancer cells in M phase. The cells were treated with allitridi became more shrunken and nepheloid, in which the microtubule networks disappeared, while the control cell exhibited an intact microtubule network. Contrasting with normal existence mainly in the cytoplasm, the cyclin B1 was expressed more significantly and concentrated in the nucleus after exposure to allitridi. Fluorescence intensity of cyclin B 1 protein in cells treated with allitridi was much more higher than that of control （P〈0.001）. Conclusion： Allitridican induce arrest of SGC-7901 cells in M phase, probably through enhancing microtubule depolymerization by elevating the expression of cyclin B1.展开更多
核膜在细胞周期中呈现高度的动态性:在细胞分裂的前中期,核膜崩解并分散到细胞质中;在细胞分裂的后期,核膜开始在染色体的表面重新装配,最终形成完整的核膜结构。近期的研究发现,Ran GTP酶、物质转运蛋白importinβ、内层核膜蛋白LBR(la...核膜在细胞周期中呈现高度的动态性:在细胞分裂的前中期,核膜崩解并分散到细胞质中;在细胞分裂的后期,核膜开始在染色体的表面重新装配,最终形成完整的核膜结构。近期的研究发现,Ran GTP酶、物质转运蛋白importinβ、内层核膜蛋白LBR(lamin B receptor)以及核孔复合体蛋白nucleoporins在核膜重建的过程中起关键性调控作用,并受到细胞周期调控因子p34cdc2激酶的调节。LBR是一个八次跨膜的膜蛋白,主要定位于内层核膜。在细胞分裂的早期,随着核膜崩解,LBR与核膜崩解而生成的小膜泡一起分散到细胞质中;在细胞分裂的后期,通过LBR与importinβ相互结合,含有LBR的膜泡被importinβ携带至染色质的表面参与核膜重建。目前已知p34cdc2激酶对LBR与importinβ介导的核膜重建起重要调控作用。Nucleoporins是核孔复合体主要组分。随核膜崩解,核孔复合体解聚成nucleoporins,分散到细胞质中,或结合到其他亚细胞成分上。细胞分裂后期,核孔复合体伴随核膜装配而组装。展开更多
基金the National NaturalScience Foundation of China (Serial No.3 980 0 1 49)
文摘Silencing ATM gene gave rise to enhanced apoptotic response to irradiation and i rradiation like chemotherapy agents, this paper explored the crucial identities of the molecular elements responsible for the enhanced apoptotic response in U937 cells mediated by silencing ATM gene. Two U937 cell mutants named U937 ASPI3K (ATM, negative) and U937 pZeosv2(+) (ATM, wild type) were used as a cell model system to identify the critical molecule(s) responsible for the varied apoptotic response in the absence or presence of ATM gene. Apoptosis was examined by measuring concentrations of free nucleosome in U937 cells. Western blot was employed to measure nuclear protein abundance of CDC25A, CDC25B, CDC25C, total p34cdc2, p34cdc2 (Thr 161) or p34cdc2 (Thr 14,Tyr 15). RT PCR was used to estimate CDC25 transcript levels. U937 ASPI3K exhibited an enhanced apoptotic response to lower dosage of irradiation, which could not be blocked by protein synthesis inhibitor. Protein serine threonine phosphatase inhibitor or cyclin dependent kinase (CDK) inhibitors, on the other hand, abolished the enhancement indicated that protein phosphorylation/dephosphorylation modification and CDK activity are required for the enhanced apoptotic response in the absence of ATM gene. Upon irradiation, p34cdc2 in U937 pZeosv2 (+) was maintained in an inactive state by phosphorylation on threonine 14 (Thr 14) and tyrosine 15 (Tyr 15), which was associated with a dramatic decrease of nuclear CDC25A, CDC25B and CDC25C proteins. In contrast, p34cdc2 in U937 ASPI3K maintained in an active state by dephosphorylation on threonine 14 (Thr 14) and tyrosine 15 (Tyr 15), which was associated with constant nuclear CDC25A, CDC25B and CDC25C protein abundance before and after irradiation. The responsive decrease of nuclear CDC25 proteins occurred at the post transcription level. Silencing ATM gene blocks the responsive decrease of nuclear CDC25 proteins, which is responsible for failure to inactivate p34cdc2 after irradiation. Active p34cdc2 and CDK2, in turn, acts as the death executors to trigger apoptosis. In abstract, aberrantly activated CDK activity is the critical molecular mechanism central to enhanced apoptotic responses in the absence of ATM gene.
基金the National 10th Five-year Plan Key Technologies R & D Program of China(No.2004BA703B04-02)
文摘Objective： To learn the effect of allitridi on inducing mitotic arrest in human gastric cell line SGC-7901 and its possible mechanisms. Methods： We treated SGC-7901 cells with allitridi, and observed the proliferation inhibitory rate with MTT colometric assay, changes of cell cycle using flow cytometry and Switzerland-Giemsa＇s staining, and morphologic changes of the microtubule structure and location changes of cyclin BI expression using immunofluorescence and confocal laser scanning microscope. Furthermore, the expression of cyclin B1 was analyzed quantitatively using Leica confocal software. Results： SGC-7901 cells were inhibited after exposure to allitridi and the IC50 was 7.2μg/ml for 24 h, 20μg/ml for 72 h. When the cells were treated with allitridi at concentrations of 3, 6, and 9μg/ml for 24 h respectively, there was a declining tendency in the percentage of G0/G1 cell but an increasing tendency in GE/M cell in the allitridi treated group compared with that of control （P〈0.01）. When cells were treated allitridi at concentration of 6 μg/ml for 24 h, its mitotic index was much higher （P〈0.01） than that of control, suggesting that allitridi caused arrest of gastric cancer cells in M phase. The cells were treated with allitridi became more shrunken and nepheloid, in which the microtubule networks disappeared, while the control cell exhibited an intact microtubule network. Contrasting with normal existence mainly in the cytoplasm, the cyclin B1 was expressed more significantly and concentrated in the nucleus after exposure to allitridi. Fluorescence intensity of cyclin B 1 protein in cells treated with allitridi was much more higher than that of control （P〈0.001）. Conclusion： Allitridican induce arrest of SGC-7901 cells in M phase, probably through enhancing microtubule depolymerization by elevating the expression of cyclin B1.
文摘核膜在细胞周期中呈现高度的动态性:在细胞分裂的前中期,核膜崩解并分散到细胞质中;在细胞分裂的后期,核膜开始在染色体的表面重新装配,最终形成完整的核膜结构。近期的研究发现,Ran GTP酶、物质转运蛋白importinβ、内层核膜蛋白LBR(lamin B receptor)以及核孔复合体蛋白nucleoporins在核膜重建的过程中起关键性调控作用,并受到细胞周期调控因子p34cdc2激酶的调节。LBR是一个八次跨膜的膜蛋白,主要定位于内层核膜。在细胞分裂的早期,随着核膜崩解,LBR与核膜崩解而生成的小膜泡一起分散到细胞质中;在细胞分裂的后期,通过LBR与importinβ相互结合,含有LBR的膜泡被importinβ携带至染色质的表面参与核膜重建。目前已知p34cdc2激酶对LBR与importinβ介导的核膜重建起重要调控作用。Nucleoporins是核孔复合体主要组分。随核膜崩解,核孔复合体解聚成nucleoporins,分散到细胞质中,或结合到其他亚细胞成分上。细胞分裂后期,核孔复合体伴随核膜装配而组装。
