Recent evidence has suggested that Akt2 plays an important role in the protection of cells from paclitaxel （PTX）-induced apoptosis and control of the cell cycle. In addition, some scholars suggested that the PTX sen...Recent evidence has suggested that Akt2 plays an important role in the protection of cells from paclitaxel （PTX）-induced apoptosis and control of the cell cycle. In addition, some scholars suggested that the PTX sensitivity depends on a functional spindle assembly checkpoint. In the present study, we investigated the role of the Akt2/Bubl cross-talking in apoptosis and cell cycle after exposure of the A2780 ovarian cancer cells to paclitaxel （PTX）. Recombinant expression plasmid WT-Akt2 was transfected into A2780 cells by lipofectamine2000, and then the expression level of Akt2 gene was detected by using RT-PCR and Western blotting. Cell apoptosis and cell cycle were detected by flow cytometry and Hoechst 33342 staining after treatment with PTX. Moreover, we compared the expression level of Bubl in different groups by Western blotting. Our study showed that up-regulation of Akt2 contributed to A2780 ovarian cancer cells overriding PTX-induced G2/M arrest, and inhibited Bubl expression. Our findings might shed light on the molecular mechanism of PTX-induced resistance in ovarian cancer and help develop novel anti-neoplastic strategies.展开更多
Error-free mitosis depends on accurate chromosome attachment to spindle microtubules,which is monitored by the spindle assembly checkpoint(SAC)signaling.As an upstream factor of SAC,the precise and dynamic kinetochore...Error-free mitosis depends on accurate chromosome attachment to spindle microtubules,which is monitored by the spindle assembly checkpoint(SAC)signaling.As an upstream factor of SAC,the precise and dynamic kinetochore localization of Mps1 kinase is critical for initiating and silencing SAC signaling.However,the underlying molecular mechanism remains elusive.Here,we demonstrated that the multisite interactions between Mps1 and Ndc80 complex(Ndc80C)govern Mps1 kinetochore targeting.Importantly,we identified direct interaction between Mps1 tetratricopeptide repeat domain and Ndc80C.We further identified that Mps1 C-terminal fragment,which contains the protein kinase domain and C-tail,enhances Mps1 kinetochore localization.Mechanistically,Mps1 C-terminal fragment mediates its dimerization.Perturbation of C-tail attenuates the kinetochore targeting and activity of Mps1,leading to aberrant mitosis due to compromised SAC function.Taken together,our study highlights the importance of Mps1 dimerization and multisite interactions with Ndc80C in enabling responsive SAC signaling.展开更多
Loss or gain of chromosomes,a condition known as aneuploidy,is a common feature of tumor cells and has therefore been proposed as the driving force for tumorigenesis.Such chromosomal instability can arise during mitos...Loss or gain of chromosomes,a condition known as aneuploidy,is a common feature of tumor cells and has therefore been proposed as the driving force for tumorigenesis.Such chromosomal instability can arise during mitosis as a result of mis-segregation of the duplicated sister chromatids to the two daughter cells.In normal cells,missegregation is usually prevented by the spindle assembly checkpoint(SAC),a sophisticated surveillance mechanism that inhibits mitotic exit until all chromosomes have successfully achieved bipolar attachment to spindle microtubules.Complete abrogation of SAC activity is lethal to normal as well as to tumor cells,as a consequence of massive chromosome mis-segregation.Importantly,many human aneuploid tumor cells exhibit a weakened SAC activity that allows them to tolerate gains or losses of a small number of chromosomes;and interfering with this SAC residual activity may constitute a suitable strategy to kill cancer cells.This review focuses on the potential link between SAC and tumorigenesis,and the therapeutic strategy to target the SAC for cancer treatment.展开更多
Chromosome segregation is a tightly regulated process through which duplicated genetic materials are equally partitioned into daughter cells. During the past decades, tremendous efforts have been made to understand th...Chromosome segregation is a tightly regulated process through which duplicated genetic materials are equally partitioned into daughter cells. During the past decades, tremendous efforts have been made to understand the molecular mechanism of chromosome segregation using animals and yeasts as model systems. Recently, new insights into chromosome segregation have gradually emerged using trypanosome, an early branching parasitic protozoan, as a model organism. To uncover the unique aspects of chromosome segregation in trypanosome, which potentially could serve as new drug targets for anti-trypanosome chemotherapy, it is necessary to perform a comparative analysis of the chromosome segregation machinery between trypanosome and its human host. Here, we briefly review the current knowledge about chromosome segregation in human and Trypanosoma brucei, with a focus on the regulation of cohesin and securin degradation triggered by the activation of the anaphase promoting complex/cyclosome （APC/C）. We also include yeasts in our comparative analysis since some of the original discoveries were made using budding and fission yeasts as the model organisms and, therefore, these could provide hints about the evolution of the machinery. We highlight both common and unique features in these model systems and also provide perspectives for future research in trypanosome.展开更多
The Bub1 and BubR1 kinetochore proteins support proper chromosome segregation and mitotic checkpoint activity. Bub1 and BubR1 are paralogs with Bub1 being a kinase, while BubR1 localizes the PP2A-B56 protein phosphata...The Bub1 and BubR1 kinetochore proteins support proper chromosome segregation and mitotic checkpoint activity. Bub1 and BubR1 are paralogs with Bub1 being a kinase, while BubR1 localizes the PP2A-B56 protein phosphatase to kinetochores in humans. Whether this spatial separation of kinase and phosphatase activity is important is unclear as some organisms integrate both activities into one Bub protein. Here, we engineer human Bub1 and BubR1 proteins integrating kinase and phosphatase activities into one protein and show that these do not support normal mitotic progression. A Bub1–PP2A-B56 complex can support chromosome alignment but results in impairment of the checkpoint due to dephosphorylation of the Mad1 binding site in Bub1. Furthermore, a chimeric BubR1 protein containing the Bub1 kinase domain induces delocalized H2ApT120 phosphorylation, resulting in the reduction of centromeric hSgo2 and chromosome segregation errors. Collectively, these results argue that the spatial separation of kinase and phosphatase activities within the Bub complex is required for balancing its functions in the checkpoint and chromosome alignment.展开更多
基金supported by Joint Research Fund for Young Scholars Abroad (No. 30528012)National Key Basic Research Program (Program 973) Foundation of China (No. 2009CB521800)
文摘Recent evidence has suggested that Akt2 plays an important role in the protection of cells from paclitaxel （PTX）-induced apoptosis and control of the cell cycle. In addition, some scholars suggested that the PTX sensitivity depends on a functional spindle assembly checkpoint. In the present study, we investigated the role of the Akt2/Bubl cross-talking in apoptosis and cell cycle after exposure of the A2780 ovarian cancer cells to paclitaxel （PTX）. Recombinant expression plasmid WT-Akt2 was transfected into A2780 cells by lipofectamine2000, and then the expression level of Akt2 gene was detected by using RT-PCR and Western blotting. Cell apoptosis and cell cycle were detected by flow cytometry and Hoechst 33342 staining after treatment with PTX. Moreover, we compared the expression level of Bubl in different groups by Western blotting. Our study showed that up-regulation of Akt2 contributed to A2780 ovarian cancer cells overriding PTX-induced G2/M arrest, and inhibited Bubl expression. Our findings might shed light on the molecular mechanism of PTX-induced resistance in ovarian cancer and help develop novel anti-neoplastic strategies.
基金supported by the National Key R&D Program of China(2017YFA 0102900 and 2017 YFA 0503600)the National Natural Science Fondation of China(31671407 and 31871359 to Z.D.+4 种基金31621002,31430054,91854203,and 31320103904 to X.Y.31301099 and 21672201 to X.G.31471275 to D.W.),Strategic Priority Research Program of the Chinese Academy of Sciences(XDB19040000)Chinese Academy of Sciences Center for Excellence in Molecular Cell Science(2015 HSC-UE010)MOE Innovative Team(IRT_17R102).
文摘Error-free mitosis depends on accurate chromosome attachment to spindle microtubules,which is monitored by the spindle assembly checkpoint(SAC)signaling.As an upstream factor of SAC,the precise and dynamic kinetochore localization of Mps1 kinase is critical for initiating and silencing SAC signaling.However,the underlying molecular mechanism remains elusive.Here,we demonstrated that the multisite interactions between Mps1 and Ndc80 complex(Ndc80C)govern Mps1 kinetochore targeting.Importantly,we identified direct interaction between Mps1 tetratricopeptide repeat domain and Ndc80C.We further identified that Mps1 C-terminal fragment,which contains the protein kinase domain and C-tail,enhances Mps1 kinetochore localization.Mechanistically,Mps1 C-terminal fragment mediates its dimerization.Perturbation of C-tail attenuates the kinetochore targeting and activity of Mps1,leading to aberrant mitosis due to compromised SAC function.Taken together,our study highlights the importance of Mps1 dimerization and multisite interactions with Ndc80C in enabling responsive SAC signaling.
基金H.B.was supported by grant#04-GBMC-CICS-09,from CESPU–Cooperativa de Ensino Superior Politécnico e Universitário.
文摘Loss or gain of chromosomes,a condition known as aneuploidy,is a common feature of tumor cells and has therefore been proposed as the driving force for tumorigenesis.Such chromosomal instability can arise during mitosis as a result of mis-segregation of the duplicated sister chromatids to the two daughter cells.In normal cells,missegregation is usually prevented by the spindle assembly checkpoint(SAC),a sophisticated surveillance mechanism that inhibits mitotic exit until all chromosomes have successfully achieved bipolar attachment to spindle microtubules.Complete abrogation of SAC activity is lethal to normal as well as to tumor cells,as a consequence of massive chromosome mis-segregation.Importantly,many human aneuploid tumor cells exhibit a weakened SAC activity that allows them to tolerate gains or losses of a small number of chromosomes;and interfering with this SAC residual activity may constitute a suitable strategy to kill cancer cells.This review focuses on the potential link between SAC and tumorigenesis,and the therapeutic strategy to target the SAC for cancer treatment.
文摘Chromosome segregation is a tightly regulated process through which duplicated genetic materials are equally partitioned into daughter cells. During the past decades, tremendous efforts have been made to understand the molecular mechanism of chromosome segregation using animals and yeasts as model systems. Recently, new insights into chromosome segregation have gradually emerged using trypanosome, an early branching parasitic protozoan, as a model organism. To uncover the unique aspects of chromosome segregation in trypanosome, which potentially could serve as new drug targets for anti-trypanosome chemotherapy, it is necessary to perform a comparative analysis of the chromosome segregation machinery between trypanosome and its human host. Here, we briefly review the current knowledge about chromosome segregation in human and Trypanosoma brucei, with a focus on the regulation of cohesin and securin degradation triggered by the activation of the anaphase promoting complex/cyclosome （APC/C）. We also include yeasts in our comparative analysis since some of the original discoveries were made using budding and fission yeasts as the model organisms and, therefore, these could provide hints about the evolution of the machinery. We highlight both common and unique features in these model systems and also provide perspectives for future research in trypanosome.
基金supported by the National Natural Science Foundation of China(31970666)Taishan Scholar Project(tsqn201812054)from Shandong,China+3 种基金Work at the Novo Nordisk Foundation Center for Protein Research was supported by the grant NNF14CC0001J.N.is supported by grants from the Danish Cancer Society(R269-A15586-B17)Independent Research Fund Denmark(8021-00101B and 0134-00199B)Novo Nordisk Foundation(NNF20OC0065098).
文摘The Bub1 and BubR1 kinetochore proteins support proper chromosome segregation and mitotic checkpoint activity. Bub1 and BubR1 are paralogs with Bub1 being a kinase, while BubR1 localizes the PP2A-B56 protein phosphatase to kinetochores in humans. Whether this spatial separation of kinase and phosphatase activity is important is unclear as some organisms integrate both activities into one Bub protein. Here, we engineer human Bub1 and BubR1 proteins integrating kinase and phosphatase activities into one protein and show that these do not support normal mitotic progression. A Bub1–PP2A-B56 complex can support chromosome alignment but results in impairment of the checkpoint due to dephosphorylation of the Mad1 binding site in Bub1. Furthermore, a chimeric BubR1 protein containing the Bub1 kinase domain induces delocalized H2ApT120 phosphorylation, resulting in the reduction of centromeric hSgo2 and chromosome segregation errors. Collectively, these results argue that the spatial separation of kinase and phosphatase activities within the Bub complex is required for balancing its functions in the checkpoint and chromosome alignment.
