RESUMO
MCM7, a subunit of mini-chromosome maintenance proteins (MCM) complex, plays an important role in initiating DNA replication during the G1 phase and extending DNA strands during the S phase. Here, we demonstrated that MCM7 is not only sustained but maintains association with chromatin during M phase. Remarkably, MCM7 siRNA can accelerate mitotic exit. MCM7 depletion leads to CDK1 inactivation and promotes subsequent cohesin/RAD21 cleavage, which eventually leads to sister chromatin segregation. Moreover, MCM7 is co-localized with tubulin in the mitotic cells and MCM7 depletion results in aberrant mitosis. Our results indicate that MCM7 may exert certain functions on spindle formation to prevent cytokinesis during early mitosis by regulating CDK1 activity.
Assuntos
Proteína Quinase CDC2/antagonistas & inibidores , Proteína Quinase CDC2/metabolismo , Componente 7 do Complexo de Manutenção de Minicromossomo/metabolismo , Mitose , Ciclo Celular/genética , Linhagem Celular Tumoral , Cromatina/genética , Cromatina/metabolismo , Expressão Gênica , Humanos , Componente 4 do Complexo de Manutenção de Minicromossomo/metabolismo , Componente 6 do Complexo de Manutenção de Minicromossomo/metabolismo , Componente 7 do Complexo de Manutenção de Minicromossomo/genética , RNA Mensageiro/genéticaRESUMO
Paclitaxel (PTX) is an antimitotic drug that possesses potent anticancer activity, but its therapeutic potential in the clinic has been hindered by drug resistance. Here, we report a mechanism by which cancer cells can exit from the PTX-induced mitotic arrest, i.e. mitotic slippage, and avoid subsequent death resulting in drug resistance. In cells experiencing mitotic slippage, Cdc6 protein level was significantly upregulated, Cdk1 activity was inhibited, and Cohesin/Rad21 was cleaved as a result. Cdc6 depletion by RNAi or Norcantharidin inhibited PTX-induced Cdc6 up-regulation, maintained Cdk1 activity, and repressed Cohesin/Rad21 cleavage. In all, this resulted in reduced mitotic slippage and reversal of PTX resistance. Moreover, in synchronized cells, the role of Cdc6 in mitotic exit under PTX pressure was also confirmed. This study indicates that Cdc6 may promote mitotic slippage by inactivation of Cdk1. Targeting of Cdc6 may serve as a promising strategy for enhancing the anticancer activity of PTX.
Assuntos
Proteínas de Ciclo Celular/metabolismo , Quinases Ciclina-Dependentes/metabolismo , Proteínas Nucleares/metabolismo , Apoptose/efeitos dos fármacos , Apoptose/genética , Western Blotting , Proteína Quinase CDC2 , Ciclo Celular/efeitos dos fármacos , Ciclo Celular/genética , Proteínas de Ciclo Celular/genética , Linhagem Celular Tumoral , Quinases Ciclina-Dependentes/genética , Resistencia a Medicamentos Antineoplásicos/genética , Citometria de Fluxo , Imunofluorescência , Humanos , Mitose/efeitos dos fármacos , Mitose/genética , Proteínas Nucleares/genética , Paclitaxel , RNA Interferente Pequeno/genéticaRESUMO
High activation of DNA damage response is implicated in cisplatin (CDDP) resistance which presents as a serious obstacle for bladder cancer treatment. Cdc6 plays an important role in the malignant progression of tumor. Here, we reported that Cdc6 expression is up-regulated in bladder cancer tissues and is positively correlated to high tumor grade. Cdc6 depletion can attenuate the malignant properties of bladder cancer cells, including DNA replication, migration and invasion. Furthermore, higher levels of chromatin-binding Cdc6 and ATR were detected in CDDP-resistant bladder cancer cells than in the parent bladder cancer cells. Intriguingly, down-regulation of Cdc6 can enhance sensitivity to CDDP both in bladder cancer cells and CDDP-resistant bladder cancer cells. Cdc6 depletion abrogates S phase arrest caused by CDDP, leading to aberrant mitosis by inactivating ATR-Chk1-Cdc25C pathway. Our results indicate that Cdc6 may be a promising target for overcoming CDDP resistance in bladder cancer.