Degradation of the Human Mitotic Checkpoint Kinase Mps1 Is Cell Cycle-regulated by APC-cCdc20 and APC-cCdh1 Ubiquitin Ligases |
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Authors: | Yongping Cui Xiaolong Cheng Ce Zhang Yanyan Zhang Shujing Li Chuangui Wang Thomas M Guadagno |
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Institution: | From the ‡Key Laboratory of Cellular Physiology, Ministry of Education.;the §Department of Cell Biology and Genetics, and ;the ¶Department of Anatomy, Shanxi Medical University, Taiyuan, Shanxi 030001, China.;the ‖School of Life Science, East China Normal University, Shanghai 200062, China, and ;the **Department of Molecular Oncology, H. Lee Moffitt Cancer Center and Research Institute, Tampa, Florida 33612 |
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Abstract: | Mps1 is a dual specificity protein kinase with key roles in regulating the spindle assembly checkpoint and chromosome-microtubule attachments. Consistent with these mitotic functions, Mps1 protein levels fluctuate during the cell cycle, peaking at early mitosis and abruptly declining during mitotic exit and progression into the G1 phase. Although evidence in budding yeast indicates that Mps1 is targeted for degradation at anaphase by the anaphase-promoting complex (APC)-cCdc20 complex, little is known about the regulatory mechanisms that govern Mps1 protein levels in human cells. Here, we provide evidence for the ubiquitin ligase/proteosome pathway in regulating human Mps1 levels during late mitosis through G1 phase. First, we showed that treatment of HEK 293T cells with the proteosome inhibitor MG132 resulted in an increase in both the polyubiquitination and the accumulation of Mps1 protein levels. Next, Mps1 was shown to co-precipitate with APC and its activators Cdc20 and Cdh1 in a cell cycle-dependent manner. Consistent with this, overexpression of Cdc20 or Cdh1 led to a marked reduction of endogenous Mps1 levels during anaphase or G1 phase, respectively. In contrast, depletion of Cdc20 or Cdh1 by RNAi treatment both led to the stabilization of Mps1 protein during mitosis or G1 phase, respectively. Finally, we identified a single D-box motif in human Mps1 that is required for its ubiquitination and degradation. Failure to appropriately degrade Mps1 is sufficient to trigger centrosome amplification and mitotic abnormalities in human cells. Thus, our results suggest that the sequential actions of the APC-cCdc20 and APC-cCdh1 ubiquitin ligases regulate the clearance of Mps1 levels and are critical for Mps1 functions during the cell cycle in human cells. |
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Keywords: | Mitosis Proteasome Protein Degradation siRNA Ubiquitin Cdc20 Cdh1 Mps1 |
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