Unknown,Transcriptomics,Genomics,Proteomics

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Foxp3 is a key downstream regulator of p53-mediated cellular senescence

ABSTRACT: The downstream events and target genes of p53 in senescence responses are not fully understood. Here, we report a novel function of the forkhead transcription factor Foxp3, a key player in mediating T cell inhibitory function, in p53-mediated cellular senescence. Overexpression of Foxp3 in mouse embryonic fibroblasts (MEFs) accelerates senescence, whereas Foxp3 knockdown leads to escape from p53-mediated senescence in p53-expressing MEFs. Consistently, Foxp3 expression resulted in the induction of senescence in epithelial cancer cells, including MCF7 and HCT116. Foxp3 overexpression also increased the intracellular levels of reactive oxygen species (ROS). The ROS inhibitor N-acetyl-L-cysteine rescued Foxp3 expression-induced senescence. Furthermore, the elevated ROS levels that accompanied Foxp3 overexpression were paralleled by an increase in p21 expression. Knockdown of p21 in Foxp3-expressing MEFs abrogated the Foxp3-dependent increase in ROS levels, indicating that Foxp3 acts through p21 induction and subsequent ROS elevation to trigger senescence. Collectively, these results suggest that Foxp3 is a downstream target of p53 that is sufficient to induce p21 expression and ROS production and is necessary for p53-mediated senescence. control and treated samples (human), young passage (p3) or old passage (p7) samples (mouse)

ORGANISM(S): Mus musculus

SUBMITTER: Dong-Hoon Jin

PROVIDER: E-GEOD-71980 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Cellular senescence is a program of irreversible cell cycle arrest that normal cells undergo in response to progressive shortening of telomeres, changes in telomeric structure, oncogene activation or oxidative stress. The underlying signalling pathways, potentially of major clinicopathological relevance, are unknown. A major stumbling block to studying senescence has been the absence of suitable model systems because of the asynchrony of this process in heterogeneous cell populations. To simplify this process many investigators study oncogene-induced senescence due to expression of activated oncogenes where senescence occurs prematurely without telomere attrition and can be induced acutely in a variety of cell types. We have taken a different approach by making use of the finding that reconstitution of telomerase activity by introduction of the catalytic subunit of human telomerase alone is incapable of immortalising all human somatic cells, but inactivation of the p16-pRB and p53-p21 pathways are required in addition. The ability of SV40 large T antigen to inactivate the p16-pRB and p53-p21 pathways has enabled us to use a thermolabile mutant of LT antigen, in conjunction with hTERT, to develop conditionally immortalised human (HMF3A) fibroblasts that are immortal but undergo an irreversible growth arrest when the thermolabile LT antigen is inactivated leading to activation of pRB and p53. When these cells cease dividing, senescence-associated- b-galactosidase activity is induced and the growth-arrested cells have morphological features and express genes in common with senescent cells. Since these cells growth arrest in a synchronous manner they are an excellent starting point for dissecting the pathways that underlie cellular senescence and act downstream of p16-pRB and p53-p21 pathways. We have combined genome-wide expression profiling with genetic complementation to undertake identification of genes that are differentially expressed when these conditionally immortalised human fibroblasts undergo senescence upon activation of the p16-pRB and p53-p21 tumour suppressor pathways. Genes differentially expressed upon senescence will be identified by comparing arrays from growing versus senescent cells. Changes in gene expression due to the temperature shift will be eliminated by comparing with array data from the non-conditional HMF3S cells grown at 34°C ±0.5°C and 38°C ±0.5°C. To determine if the changes in gene expression upon senescence are specific and reversible, the set of differential genes will then be overlaid with array data from cells in which senescence has been bypassed by inactivation of the p16-pRB and p53-p21 tumour suppressor pathways

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Foxp3 is a key downstream regulator of p53-mediated cellular senescence

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