Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:2.7.11.22 (cdc2)
 8,319 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

p53 protects mammals from neoplasia by inducing apoptosis, DNA repair and cell cycle arrest in response to a variety of stresses. p53-dependent arrest of cells in the G1 phase of the cell cycle is an important component of the cellular response to stress. Here we review recent evidence that implicates p53 in controlling entry into mitosis when cells enter G2 with damaged DNA or when they are arrested in S phase due to depletion of the substrates required for DNA synthesis. Part of the mechanism by which p53 blocks cells at the G2 checkpoint involves inhibition of Cdc2, the cyclin-dependent kinase required to enter mitosis. Cdc2 is inhibited simultaneously by three transcriptional targets of p53, Gadd45, p21, and 14-3-3 sigma. Binding of Cdc2 to Cyclin B1 is required for its activity, and repression of the cyclin B1 gene by p53 also contributes to blocking entry into mitosis. p53 also represses the cdc2 gene, to help ensure that cells do not escape the initial block. Genotoxic stress also activates p53-independent pathways that inhibit Cdc2 activity, activation of the protein kinases Chk1 and Chk2 by the protein kinases Atm and Atr. Chk1 and Chk2 inhibit Cdc2 by inactivating Cdc25, the phosphatase that normally activates Cdc2. Chk1, Chk2, Atm and Atr also contribute to the activation of p53 in response to genotoxic stress and therefore play multiple roles. p53 induces transcription of the reprimo, B99, and mcg10 genes, all of which contribute to the arrest of cells in G2, but the mechanisms of cell cycle arrest by these genes is not known. Repression of the topoisomerase II gene by p53 helps to block entry into mitosis and strengthens the G2 arrest. In summary, multiple overlapping p53-dependent and p53-independent pathways regulate the G2/M transition in response to genotoxic stress.
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PMID:Regulation of the G2/M transition by p53. 1131 28

In response to various forms of cellular stress, including DNA damage, ribonucleotide depletion, and abnormal proliferative signals, p53 becomes activated as a transcription factor, targeted genes that induce cell-cycle arrest and apoptosis. Eliminating damaged, stressed, or abnormally proliferating cells from the replicating cell population prevents the propagation of potentially cancer-prone cells. Here we focus on the transcriptional targets of p53 that regulate the cell cycle. p53 Induction of G1/ S cell-cycle arrest is largely attributed to the transcriptional upregulation of p21WAF1, and more recently, to the transcriptional repression of c-MYC. The role of p53 in G2/M cell-cycle arrest in response to DNA damage is more complex, involving multiple targets that can generally be considered to impinge upon either the cell cycle (e.g., Cyclin-B, cdc2, cdc25C) or the mitotic machinery (i.e., Topoisomerase II, B99/Gtse-1, and MAP4). The ability of p53 to regulate these two type of gene targets may reflect p53-mediated early versus late events in the G2/M cell-cycle arrest response. Together the information presented illustrates the need for further studies to precisely delineate the nature of G2/M cell-cycle arrest in response to cell stress, and defines the role of p53 in what is likely an important mechanism of tumor suppression.
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PMID:Transcriptional targets of p53 that regulate cellular proliferation. 1736 86