Degradation of p21(Cip1) through Anaphase-promoting Complex/Cyclosome and Its Activator Cdc20 (APC/C-Cdc20) Ubiquitin Ligase Complex-mediated Ubiquitylation Is Inhibited by Cyclin-dependent Kinase 2 in Cardiomyocytes

Laboratory of Genome Structure and Regulation, School of Biomedical Science, Department of Biochemical Genetics, Medical Research Institute, Tokyo Medical and Dental University, Tokyo, Japan.
Journal of Biological Chemistry (Impact Factor: 4.57). 11/2011; 286(51):44057-66. DOI: 10.1074/jbc.M111.236711
Source: PubMed


Cyclin-dependent kinase inhibitor p21Cip1 plays a crucial role in regulating cell cycle arrest and differentiation. It is known that p21Cip1 increases during terminal differentiation of cardiomyocytes, but its expression control and biological roles are not fully
understood. Here, we show that the p21Cip1 protein is stabilized in cardiomyocytes after mitogenic stimulation, due to its increased CDK2 binding and inhibition of
ubiquitylation. The APC/CCdc20 complex is shown to be an E3 ligase mediating ubiquitylation of p21Cip1 at the N terminus. CDK2, but not CDC2, suppressed the interaction of p21Cip1 with Cdc20, thereby leading to inhibition of anaphase-promoting complex/cyclosome and its activator Cdc20 (APC/CCdc20)-mediated p21Cip1 ubiquitylation. It was further demonstrated that p21Cip1 accumulation caused G2 arrest of cardiomyocytes that were forced to re-enter the cell cycle. Taken together, these data show that the stability
of the p21Cip1 protein is actively regulated in terminally differentiated cardiomyocytes and plays a role in inhibiting their uncontrolled
cell cycle progression. Our study provides a novel insight on the control of p21Cip1 by ubiquitin-mediated degradation and its implication in cell cycle arrest in terminal differentiation.

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    • "Moreover, we found that p21 accumulated rapidly in Bat3-KD cells released from a nocodazole arrest, whereas the phosphorylation of p21 was reduced. Degradation of p21 by APC/CCdc20 during G2/M progression has also been reported to occur during prometaphase and the interaction between Cdk2 and p21 inhibits this process [17], [46]. These findings suggest that the decreased p21 phosphorylation in the Bat3-KD cells results in continuous p21 synthesis. "
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    ABSTRACT: Our study aimed to investigate the gene expression at different myocardial infarction (MI) phases and to understand the development mechanisms of congestive heart failure (CHF) after MI. Dataset GSE1957 including 24 samples of rat left ventricles at 1-day post MI or sham operation and 7-day post MI or sham operation was downloaded from Gene Expression Ominibus. The data were normalized with an affyPLM package and differentially expressed genes (DEGs) were identified with a Linear Models for Microarray Data package. Heat maps of the DEGs were constructed using Cluster 3.0. GO (Gene Ontology) enrichment analysis of the DEGs was performed in Database for Annotation, Visualization, and Integrated Discovery. A protein-protein interaction (PPI) network was constructed by Biomolecular Interaction Network Database and visualized by Cytoscape, and a subnetwork was analyzed using plugin ClusterONE in Cytoscape. A total of 5 DEGs at 1-day post-MI, 5 DEGs at 7-day post-MI, and 7 DEGs between the MI and sham groups at 1-day and 7-day post-MI were identified. For the GO category analysis, DEGs at 1-day post-MI were enriched in response to cytokine stimulus. DEGs at 7-day post-MI were enriched in response to inorganic substance and chemical homeostasis. DEGs between 1-day and 7-day post-MI including CDK2 and CDC20 were significantly enriched in mitosis. CDK2, ANXA1, CDC20, and AQP2 were included in the PPI network, and CDK2 was the only DEG included in the subnetwork. In conclusion, the induction of DEGs at 7-day post-MI might participate in the response to a hormone and endogenous stimulus to regulate the development of CHF after MI.
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