Identification of Cell Cycle Regulatory Genes as Principal Targets of p53-mediated Transcriptional Repression

Spurgers, Kevin B.; Gold, David; Coombes, Kevin R.; Bohnenstiehl, Nicole; Mullins, Brian; Meyn, Raymond E.; Logothetis, Christopher J.; McDonnell, Timothy J.

doi:10.1074/jbc.m513901200

Cited by 108 publications

(111 citation statements)

References 47 publications

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“…For simplicity, we divided these mechanisms into 3 classes and analyzed one representative mechanism from each class ( Fig. 1 A): I: G1 arrest represented by p53-dependent inhibition of cyclin E/Cdk and cyclin D/Cdk complexes by p21 (21,22); II: p53-independent G2 arrest represented by posttranslational inactivation of cyclin A/Cdk and cyclin B/Cdk complexes (23,24); and III: p53-dependent G2 arrest represented by transcriptional repression of cyclin A, cyclin B, and Cdk1 (25)(26)(27)(28). sulting network behavior ( Fig.…”

Section: Resultsmentioning

confidence: 99%

Distinct mechanisms act in concert to mediate cell cycle arrest

Toettcher

Loewer

Ostheimer

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

111

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In response to DNA damage, cells arrest at specific stages in the cell cycle. This arrest must fulfill at least 3 requirements: it must be activated promptly; it must be sustained as long as damage is present to prevent loss of genomic information; and after the arrest, cells must re-enter into the appropriate cell cycle phase to ensure proper ploidy. Multiple molecular mechanisms capable of arresting the cell cycle have been identified in mammalian cells; however, it is unknown whether each mechanism meets all 3 requirements or whether they act together to confer specific functions to the arrest. To address this question, we integrated mathematical models describing the cell cycle and the DNA damage signaling networks and tested the contributions of each mechanism to cell cycle arrest and re-entry. Predictions from this model were then tested with quantitative experiments to identify the combined action of arrest mechanisms in irradiated cells. We find that different arrest mechanisms serve indispensable roles in the proper cellular response to DNA damage over time: p53-independent cyclin inactivation confers immediate arrest, whereas p53-dependent cyclin downregulation allows this arrest to be sustained. Additionally, p21-mediated inhibition of cyclin-dependent kinase activity is indispensable for preventing improper cell cycle re-entry and endoreduplication. This work shows that in a complex signaling network, seemingly redundant mechanisms, acting in a concerted fashion, can achieve a specific cellular outcome.DNA damage ͉ dynamics ͉ mathematical model ͉ p53 ͉ cyclins O ne goal of systems biology is to quantitatively understand the dynamics of signaling pathways. As mathematical models of individual pathways emerge, we are challenged to interconnect them into a detailed understanding of how different pathways control the processing of information within the cell. The networks controlling cell cycle progression and the response to DNA damage are natural choices for such an integrative study. Each has been individually modeled successfully, and a great deal is understood about how specific interactions and regulation affect the dynamics of each network. However, in the absence of an extended model bridging these two pathways, the quantitative interaction between them remains undescribed. Here we develop a computational model of the combined networks and use it together with experimental measurements to determine the relative contribution and specific function of different cell cycle arrest mechanisms in response to DNA damage.During the cell cycle, mammalian cells coordinate cell growth, genome replication, and division. Two irreversible events subdivide the cell cycle into distinct phases: the onset of DNA replication defines S phase; and cell division defines M phase. Cells grow and carry out additional functions during the gap phases G1 and G2. The changing activity states of cyclindependent kinases (Cdks) regulate the transition between different stages of the cell cycle (1). Cyclin D/Cdk4 and -6 and cycli...

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Section: Resultsmentioning

confidence: 99%

Distinct mechanisms act in concert to mediate cell cycle arrest

Toettcher

Loewer

Ostheimer

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

111

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“…Besides its role as an activator of apoptosis and senescence-inducing genes, p53 also acts as a direct transcriptional repressor of several cell-cycle-promoting factors (St Clair et al, 2004;Banerjee et al, 2009). Moreover, through p21-dependent inhibition of CDK activity, p53 indirectly induces the formation of repressive pocket protein-E2F complexes, thereby leading to sustained transcriptional downregulation of many key enzymes of mitosis and replication (Lo¨hr et al, 2003;Jackson et al, 2005;Spurgers et al, 2006;Kidokoro et al, 2008). This negative effect on mRNA synthesis is complemented at the level of protein production by another class of p53 target genes, the miR-34 family (He et al, 2007;Hermeking, 2007).…”

Section: Introductionmentioning

confidence: 99%

p53- and p21-dependent premature APC/C–Cdh1 activation in G2 is part of the long-term response to genotoxic stress

2010

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The long-term cellular response to DNA damage is controlled by the tumor suppressor p53. It results in cellcycle arrest followed by DNA repair and, depending on the degree of damage inflicted, premature senescence or apoptotic cell death. Here we show that in normal diploid fibroblasts the ubiquitin ligase anaphase-promoting complex or cyclosome (APC/C)-Cdh1 becomes prematurely activated in G2 as part of the sustained long-term but not the rapid short-term response to genotoxic stress and results in the degradation of numerous APC/C substrates. Using HCT116 somatic knockout cells we show that mechanistically premature APC/C activation depends on p53 and its transcriptional target p21 that mediates the signal through downregulation of the APC/C inhibitor Emi1. Cdc14B is dispensable in this setting but might function redundantly. Our data suggest an unexpected role for the APC/C in executing a part of the p53-dependent DNA damage response that leads to premature senescence.

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“…4a). Repression of CDK4 and CCNE2 has previously been noted after p53 activation in PC3 cells 7 . Our results indicate the possibility that p53 might repress these genes indirectly by the induction of miR-34.…”

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confidence: 99%

A microRNA component of the p53 tumour suppressor network

Lim

et al. 2007

Nature

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A global decrease in microRNA (miRNA) levels is often observed in human cancers 1,2 , indicating that small RNAs may have an intrinsic function in tumour suppression. To identify miRNA components of tumour suppressor pathways, we compared miRNA expression profiles of wildtype and p53-deficient cells. Here we describe a family of miRNAs, miR-34a-c, whose expression reflected p53 status. Genes encoding miRNAs in the miR-34 family are direct transcriptional targets of p53, whose induction by DNA damage and oncogenic stress depends on p53 both in vitro and in vivo. Ectopic expression of miR-34 induces cell cycle arrest in both primary and tumour-derived cell lines, which is consistent with the observed ability of miR-34 to downregulate a programme of genes promoting cell cycle progression. The p53 network suppresses tumour formation through the coordinated activation of multiple transcriptional targets, and miR-34 may act in concert with other effectors to inhibit inappropriate cell proliferation.The p53 tumour suppressor lies at a nexus of cellular pathways that sense DNA damage, cellular stress and improper mitogenic stimulation 3 . p53 integrates such signals and, in response, induces growth arrest, promotes apoptosis, blocks angiogenesis, or mediates DNA repair in a context-dependent manner 4 . The importance of p53 in preventing tumour formation is indicated by the presence of mutations in the p53 pathway in nearly all cancers 5 . Although p53 is most studied as a transcriptional activator, several reports have suggested that p53 represses the expression of specific genes 6 . Studies of p53-mediated Reprints and permissions information is available at www.nature.com/reprints.

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Identification of Cell Cycle Regulatory Genes as Principal Targets of p53-mediated Transcriptional Repression

Cited by 108 publications

References 47 publications

Distinct mechanisms act in concert to mediate cell cycle arrest

Distinct mechanisms act in concert to mediate cell cycle arrest

p53- and p21-dependent premature APC/C–Cdh1 activation in G2 is part of the long-term response to genotoxic stress

A microRNA component of the p53 tumour suppressor network

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