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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 the process of senescence are not fully understood. Here, we report a novel function of the forkhead transcription factor Foxp3, which is a key player in mediating T cell inhibitory functions, in p53-mediated cellular senescence. The overexpression of Foxp3 in mouse embryonic fibroblasts (MEFs) accelerates senescence, whereas Foxp3 knockdown leads to escape from p53-mediated senescence in p53-expressing MEFs. Consistent with these results, Foxp3 expression resulted in the induction of senescence in epithelial cancer cells, including MCF7 and HCT116 cells. Foxp3 overexpression also increased the intracellular levels of reactive oxygen species (ROS). The ROS inhibitor N-acetyl-L-cysteine rescued cells from 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 the induction of p21 and the 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.

ORGANISM(S): Mus musculus Homo sapiens

PROVIDER: GSE71980 | GEO | 2015/08/13

SECONDARY ACCESSION(S): PRJNA292656

REPOSITORIES: GEO

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Project description:Recently, more than a thousand large intergenic non-coding RNAs (lincRNAs) have been reported. These RNAs are evolutionarily conserved in mammalian genomes and thus presumably function in diverse biological processes. Here, we report the identification of lincRNAs that are regulated by p53. One of these lincRNAs (lincRNA-p21) serves as a repressor in p53-dependent transcriptional responses. Inhibition of lincRNA-p21 affects the expression of hundreds of gene targets enriched for genes normally repressed by p53. The observed transcriptional repression by lincRNA-p21 is mediated through the physical association with hnRNP-K. This interaction is required for proper genomic localization of hnRNP-K at repressed genes and regulation of p53 mediated apoptosis. We propose a model whereby transcription factors activate lincRNAs that serve as key repressors by physically associating with repressive complexes and modulating their localization to sets of previously active genes. Gene expression profiles of different p53 inducible mouse embryonic fibroblasts (p53LSL/LSL MEFs) across different time points after DNA damage. A large intergenic noncoding RNA induced by p53 mediates global gene repression in the p53 transcriptional response. [1] MEF profiling: p53 LSL/LSL MEFs were treated with adenoCRE for p53 restoration or adenoGFP as control for 24h and treated with 500nM doxorubicin for the indicated times. [2] hnRNPKKD profiling: p53 LSL/LSL MEFs were treated with adenoCRE for p53 restoration for 24h, transfected with siRNA oligos targeting different transcripts for 24h and then treated with 100nM doxorubicin for 13h. [3] lincP21KD profiling: p53 LSL/LSL MEFs were treated with adenoCRE for p53 restoration for 24h, transfected with siRNA oligos targeting different transcripts for 24h and then treated with 100nM doxorubicin for 13h. [4] RAS profiling: For p53 restoration, cultured tumor cell lines were incubated with 500nM 4-hydroxytamoxifen for the indicated times.

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

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