Nuclear envelope is a dynamic structure in the cell cycle. At the beginning of mitosis, nuclear envelope breaks down and its components disperse into the cytoplasm. At the end of mitosis, nuclear envelope reassembles ...Nuclear envelope is a dynamic structure in the cell cycle. At the beginning of mitosis, nuclear envelope breaks down and its components disperse into the cytoplasm. At the end of mitosis, nuclear envelope reassembles using the dispersed components. Searching for the mechanisms of the nuclear disassembly and reassembly has for a long time been one of the key projects for cell biologists. In this report we show that microtubules take a role in the nuclear envelope assembly around the sperm chromatin in Xenopus egg ex-tracts. Microtubule cytoskeleton has been demonstrated to take roles in the transport of intracellular membranes such as Golgi and ER vesicles. We found that the nuclear envelope assembly needs functional microtubules. At the beginning of the nuclear assembly, microtubules nucleated to form a microtubule aster around the centrosome at the base of the sperm head. Using the microtubule drug colchicine to dis-rupt the microtubule nucleation, nuclear envelope reassem-bly was seriously inhibited. If the microtubules were stabi-lized by taxol, another microtubule drug, the nuclear enve-lope reassembly was also interfered, although a significantly large aster formed around the chromatin. Based on these observations, we propose that microtubules play an impor-tant role in the nuclear envelope reassembly maybe by transporting the nuclear envelope precursors to the chroma-tin surfaces.展开更多
TRAIL is a tumor necrosis factor family member that selectively induces apoptosis of cancer cells but not of normal cells. To develop TRAIL into a potential cancer drug, three different sizes of soluble TRAIL fragment...TRAIL is a tumor necrosis factor family member that selectively induces apoptosis of cancer cells but not of normal cells. To develop TRAIL into a potential cancer drug, three different sizes of soluble TRAIL fragments, including sTRAIL(74 - 281), sTRAIL(95 - 281) and sTRAIL(101-281), were expressed in E. coli and purified to homogeneity. Apoptosis assays indicated that sTRAIL(95-281) and sTRAIL(101-281), but not sTRAIL(74-281), can potently induce apoptosis of various cancer cell lines in 6 h, suggesting that the N-terminal fragment of aa101 has inhibitory effect on TRAIL-induced apoptosis. Moreover, we found that some cancer cells were resistant to TRAIL and the resistant cells could be converted into sensitive cells by treatment with the protein synthesis inhibitor cycloheximide, suggesting that one or more short-lived proteins are responsible for cells’ resistance to TRAIL.展开更多
Menadione can induce apoptosis in tobacco protoplasts, Typical characteristics are detected including the condensation of chromatin, the formation of apoptotic bodies and the degradation of genomic DNA into 'DNA l...Menadione can induce apoptosis in tobacco protoplasts, Typical characteristics are detected including the condensation of chromatin, the formation of apoptotic bodies and the degradation of genomic DNA into 'DNA ladder'. Specific DNase is activated during this process. Ca2+ and Mg2+ are necessary for its activation, while 2n2+ and EDTA (Ethylenediaminetetraacetic acid) can inhibit its activation. The fragmentation of DNA and lamin can be inhibited by DEVD (Ac-Asp -Glu- Val- Asp-aldehyde). The fragmentation of lamin can also be inhibited by PMSF (Phenylmethylsulfonyl fluoride) and CH (Cyclohexinide). These results show that activation of specific DNase and proteases is involved in menadion-induced apoptosis in plants.展开更多
文摘Nuclear envelope is a dynamic structure in the cell cycle. At the beginning of mitosis, nuclear envelope breaks down and its components disperse into the cytoplasm. At the end of mitosis, nuclear envelope reassembles using the dispersed components. Searching for the mechanisms of the nuclear disassembly and reassembly has for a long time been one of the key projects for cell biologists. In this report we show that microtubules take a role in the nuclear envelope assembly around the sperm chromatin in Xenopus egg ex-tracts. Microtubule cytoskeleton has been demonstrated to take roles in the transport of intracellular membranes such as Golgi and ER vesicles. We found that the nuclear envelope assembly needs functional microtubules. At the beginning of the nuclear assembly, microtubules nucleated to form a microtubule aster around the centrosome at the base of the sperm head. Using the microtubule drug colchicine to dis-rupt the microtubule nucleation, nuclear envelope reassem-bly was seriously inhibited. If the microtubules were stabi-lized by taxol, another microtubule drug, the nuclear enve-lope reassembly was also interfered, although a significantly large aster formed around the chromatin. Based on these observations, we propose that microtubules play an impor-tant role in the nuclear envelope reassembly maybe by transporting the nuclear envelope precursors to the chroma-tin surfaces.
基金This study was supported by the National Natural Science Foundation of China (Grant No. 39925016) the National Basic- Science Researches Program (Grant No. G19990539) Peking Uni- versity.
文摘TRAIL is a tumor necrosis factor family member that selectively induces apoptosis of cancer cells but not of normal cells. To develop TRAIL into a potential cancer drug, three different sizes of soluble TRAIL fragments, including sTRAIL(74 - 281), sTRAIL(95 - 281) and sTRAIL(101-281), were expressed in E. coli and purified to homogeneity. Apoptosis assays indicated that sTRAIL(95-281) and sTRAIL(101-281), but not sTRAIL(74-281), can potently induce apoptosis of various cancer cell lines in 6 h, suggesting that the N-terminal fragment of aa101 has inhibitory effect on TRAIL-induced apoptosis. Moreover, we found that some cancer cells were resistant to TRAIL and the resistant cells could be converted into sensitive cells by treatment with the protein synthesis inhibitor cycloheximide, suggesting that one or more short-lived proteins are responsible for cells’ resistance to TRAIL.
文摘Menadione can induce apoptosis in tobacco protoplasts, Typical characteristics are detected including the condensation of chromatin, the formation of apoptotic bodies and the degradation of genomic DNA into 'DNA ladder'. Specific DNase is activated during this process. Ca2+ and Mg2+ are necessary for its activation, while 2n2+ and EDTA (Ethylenediaminetetraacetic acid) can inhibit its activation. The fragmentation of DNA and lamin can be inhibited by DEVD (Ac-Asp -Glu- Val- Asp-aldehyde). The fragmentation of lamin can also be inhibited by PMSF (Phenylmethylsulfonyl fluoride) and CH (Cyclohexinide). These results show that activation of specific DNase and proteases is involved in menadion-induced apoptosis in plants.
