Project description:The tumor suppressor p53 plays a crucial role in cellular growth control inducing a plethora of cellular response pathways. The molecular mechanisms that discriminate between the distinct p53-responses towards different stress treatments have remained largely elusive. Here, we have analyzed the p53-regulated pathways induced by two chemotherapeutical treatments, Actinomycin D inducing growth arrest and Etoposide resulting in apoptosis. We found that the genome-wide p53-binding patterns are almost identical upon both treatments notwithstanding transcriptional differences that we observed in genome-wide transcriptome analysis. To assess the role of post-translational modifications in target gene choice and activation we investigated the extent of phosphorylation of Serine 46 of p53 bound to DNA (p53-pS46), a modification that has been linked to apoptosis-pathways, and the extent of phosphorylation of Serine 15 (p53-pS15), a general p53-activation mark. Interestingly, the overall extent of S46 phosphorylation of p53 bound to DNA is considerably higher in cells directed towards apoptosis while the degree of phosphorylation at S15 of DNA bound p53 remains highly similar upon both treatments. Moreover, our data suggest that, following different chemotherapeutical treatments, the extent of chromatin-associated p53 phosphorylated at S46 but not at pS15 is higher on certain apoptosis related target genes, including the BAX and PUMA genes. These data provide evidence that cell fate decisions are not made primarily on the level of general p53 DNA-binding, but possibly through post-translational modifications of chromatin bound p53. ChIP-seq profiles of p53, p53phosphorylated at Serine 15 (p53-pS15) and p53 phosphorylated at Serine 46 (p53-pS46) in U2OS cells treated with either Actinomycin D or Etoposide.
Project description:The tumor suppressor p53 plays a crucial role in cellular growth control inducing a plethora of cellular response pathways. The molecular mechanisms that discriminate between the distinct p53-responses towards different stress treatments have remained largely elusive. Here, we have analyzed the p53-regulated pathways induced by two chemotherapeutical treatments, Actinomycin D inducing growth arrest and Etoposide resulting in apoptosis. We found that the genome-wide p53-binding patterns are almost identical upon both treatments notwithstanding transcriptional differences that we observed in genome-wide transcriptome analysis. To assess the role of post-translational modifications in target gene choice and activation we investigated the extent of phosphorylation of Serine 46 of p53 bound to DNA (p53-pS46), a modification that has been linked to apoptosis-pathways, and the extent of phosphorylation of Serine 15 (p53-pS15), a general p53-activation mark. Interestingly, the overall extent of S46 phosphorylation of p53 bound to DNA is considerably higher in cells directed towards apoptosis while the degree of phosphorylation at S15 of DNA bound p53 remains highly similar upon both treatments. Moreover, our data suggest that, following different chemotherapeutical treatments, the extent of chromatin-associated p53 phosphorylated at S46 but not at pS15 is higher on certain apoptosis related target genes, including the BAX and PUMA genes. These data provide evidence that cell fate decisions are not made primarily on the level of general p53 DNA-binding, but possibly through post-translational modifications of chromatin bound p53. Microarray analysis (Affymetrix Human Exon array) of the p53 response in U2OS cells treated with either Etoposide or Actinomycin D
Project description:The tumor suppressor p53 plays a crucial role in cellular growth control inducing a plethora of cellular response pathways. The molecular mechanisms that discriminate between the distinct p53-responses towards different stress treatments have remained largely elusive. Here, we have analyzed the p53-regulated pathways induced by two chemotherapeutical treatments, Actinomycin D inducing growth arrest and Etoposide resulting in apoptosis. We found that the genome-wide p53-binding patterns are almost identical upon both treatments notwithstanding transcriptional differences that we observed in genome-wide transcriptome analysis. To assess the role of post-translational modifications in target gene choice and activation we investigated the extent of phosphorylation of Serine 46 of p53 bound to DNA (p53-pS46), a modification that has been linked to apoptosis-pathways, and the extent of phosphorylation of Serine 15 (p53-pS15), a general p53-activation mark. Interestingly, the overall extent of S46 phosphorylation of p53 bound to DNA is considerably higher in cells directed towards apoptosis while the degree of phosphorylation at S15 of DNA bound p53 remains highly similar upon both treatments. Moreover, our data suggest that, following different chemotherapeutical treatments, the extent of chromatin-associated p53 phosphorylated at S46 but not at pS15 is higher on certain apoptosis related target genes, including the BAX and PUMA genes. These data provide evidence that cell fate decisions are not made primarily on the level of general p53 DNA-binding, but possibly through post-translational modifications of chromatin bound p53.
Project description:The tumor suppressor p53 plays a crucial role in cellular growth control inducing a plethora of cellular response pathways. The molecular mechanisms that discriminate between the distinct p53-responses towards different stress treatments have remained largely elusive. Here, we have analyzed the p53-regulated pathways induced by two chemotherapeutical treatments, Actinomycin D inducing growth arrest and Etoposide resulting in apoptosis. We found that the genome-wide p53-binding patterns are almost identical upon both treatments notwithstanding transcriptional differences that we observed in genome-wide transcriptome analysis. To assess the role of post-translational modifications in target gene choice and activation we investigated the extent of phosphorylation of Serine 46 of p53 bound to DNA (p53-pS46), a modification that has been linked to apoptosis-pathways, and the extent of phosphorylation of Serine 15 (p53-pS15), a general p53-activation mark. Interestingly, the overall extent of S46 phosphorylation of p53 bound to DNA is considerably higher in cells directed towards apoptosis while the degree of phosphorylation at S15 of DNA bound p53 remains highly similar upon both treatments. Moreover, our data suggest that, following different chemotherapeutical treatments, the extent of chromatin-associated p53 phosphorylated at S46 but not at pS15 is higher on certain apoptosis related target genes, including the BAX and PUMA genes. These data provide evidence that cell fate decisions are not made primarily on the level of general p53 DNA-binding, but possibly through post-translational modifications of chromatin bound p53.
Project description:Our previous studies have implicated CHIP as a co-chaperone/ubiquitin ligase, whose activities yield protection against stress-induced apoptotic events. In this report, we demonstrate a stress-dependent interaction between CHIP (carboxyl terminus of Hsp70-interacting protein) and Daxx, death domain-associated protein. This interaction interferes with the stress-dependent association of HIPK2 with Daxx, blocking phosphorylation of serine 46 in p53 and inhibiting the p53-dependent apoptotic program. Microarray analysis confirmed suppression of the p53-dependent transcriptional portrait in CHIP (+/+) but not in CHIP (-/-) heat shocked MEFs. The interaction between CHIP and Daxx results in ubiquitination of Daxx which is then partitioned to an insoluble compartment of the cell. In vitro ubiquitination of Daxx by CHIP revealed that Ub chain formation utilizes non canonical lysine linkages associated with resistance to proteasomal degradation. CHIP's ubiquitination of Daxx utilizes lysines 630 and 631 and competes with the cell's sumoylation machinery at these residues. These studies implicate CHIP as a stress-dependent regulator of Daxx that counters Daxx's pro-apoptotic influence in the cell. By abrogating p53-dependent apoptotic pathways and by ubiquitination competitive with Daxx sumoylation, CHIP integrates the cell's proteotoxic stress response with cell cycle pathways that influence cell survival. Keywords: p53, apoptosis, cell stress, ubiquitination
Project description:We determined the effect of p53 activation on de novo protein synthesis using quantitative proteomics of newly synthesized proteins (pulsed stable isotope labeling with amino acids in cell culture, pSILAC) in combination with mRNA and non-coding RNA expression analyses by next generation sequencing (RNA-, miR-Seq) in the colorectal cancer (CRC) cell line SW480. Furthermore, genome-wide DNA binding of p53 was analyzed by chromatin-immunoprecipitation (ChIP-Seq). Thereby, we identified differentially regulated mRNAs (1258 up, 415 down), miRNAs (111 up, 95 down), lncRNAs (270 up, 123 down) and proteins (542 up, 569 down). Changes in mRNA and protein expression levels showed a positive correlation (r = 0.50, p < 0.0001). More transcriptionally induced genes displayed occupied p53 binding sites (4.3% mRNAs, 7.2% miRNAs, 6.3% lncRNAs, 5.9% proteins) than repressed genes (2.4% mRNAs, 3.2% miRNAs, 0.8% lncRNAs, 1.9% proteins), suggesting indirect mechanisms of repression. Around 50% of the downregulated proteins displayed seed-matching sequences of p53-induced miRNAs in the corresponding 3â??-UTRs. Moreover, proteins repressed by p53 significantly overlapped with those previously shown to be repressed by miR-34a. We confirmed upregulation of the novel direct p53 target genes LINC01021, MDFI, ST14 and miR-486 and showed that ectopic LINC01021 expression inhibited proliferation in SW480 cells. Furthermore, HMGB1, KLF12 and CIT mRNAs were confirmed as direct targets of the p53-induced miR-34a, miR-205 and miR-486-5p, respectively. In line with the loss of p53 function during tumor progression, elevated expression of HMGB1, KLF12 and CIT was detected in advanced stages of cancer. This study provides new insights and a comprehensive catalogue of p53-mediated regulations and p53 DNA binding in CRC cells.
Project description:We determined the effect of p53 activation on de novo protein synthesis using quantitative proteomics of newly synthesized proteins (pulsed stable isotope labeling with amino acids in cell culture, pSILAC) in combination with mRNA and non-coding RNA expression analyses by next generation sequencing (RNA-, miR-Seq) in the colorectal cancer (CRC) cell line SW480. Furthermore, genome-wide DNA binding of p53 was analyzed by chromatin-immunoprecipitation (ChIP-Seq). Thereby, we identified differentially regulated mRNAs (1258 up, 415 down), miRNAs (111 up, 95 down), lncRNAs (270 up, 123 down) and proteins (542 up, 569 down). Changes in mRNA and protein expression levels showed a positive correlation (r = 0.50, p < 0.0001). More transcriptionally induced genes displayed occupied p53 binding sites (4.3% mRNAs, 7.2% miRNAs, 6.3% lncRNAs, 5.9% proteins) than repressed genes (2.4% mRNAs, 3.2% miRNAs, 0.8% lncRNAs, 1.9% proteins), suggesting indirect mechanisms of repression. Around 50% of the downregulated proteins displayed seed-matching sequences of p53-induced miRNAs in the corresponding 3’-UTRs. Moreover, proteins repressed by p53 significantly overlapped with those previously shown to be repressed by miR-34a. We confirmed upregulation of the novel direct p53 target genes LINC01021, MDFI, ST14 and miR-486 and showed that ectopic LINC01021 expression inhibited proliferation in SW480 cells. Furthermore, HMGB1, KLF12 and CIT mRNAs were confirmed as direct targets of the p53-induced miR-34a, miR-205 and miR-486-5p, respectively. In line with the loss of p53 function during tumor progression, elevated expression of HMGB1, KLF12 and CIT was detected in advanced stages of cancer. This study provides new insights and a comprehensive catalogue of p53-mediated regulations and p53 DNA binding in CRC cells.
Project description:Our previous studies have implicated CHIP as a co-chaperone/ubiquitin ligase, whose activities yield protection against stress-induced apoptotic events. In this report, we demonstrate a stress-dependent interaction between CHIP (carboxyl terminus of Hsp70-interacting protein) and Daxx, death domain-associated protein. This interaction interferes with the stress-dependent association of HIPK2 with Daxx, blocking phosphorylation of serine 46 in p53 and inhibiting the p53-dependent apoptotic program. Microarray analysis confirmed suppression of the p53-dependent transcriptional portrait in CHIP (+/+) but not in CHIP (-/-) heat shocked MEFs. The interaction between CHIP and Daxx results in ubiquitination of Daxx which is then partitioned to an insoluble compartment of the cell. In vitro ubiquitination of Daxx by CHIP revealed that Ub chain formation utilizes non canonical lysine linkages associated with resistance to proteasomal degradation. CHIP's ubiquitination of Daxx utilizes lysines 630 and 631 and competes with the cell's sumoylation machinery at these residues. These studies implicate CHIP as a stress-dependent regulator of Daxx that counters Daxx's pro-apoptotic influence in the cell. By abrogating p53-dependent apoptotic pathways and by ubiquitination competitive with Daxx sumoylation, CHIP integrates the cell's proteotoxic stress response with cell cycle pathways that influence cell survival. Keywords: p53, apoptosis, cell stress, ubiquitination We utilized a âsample x referenceâ experimental design strategy in which RNA extracted from mouse embryonic fibroblasts was hybridized to the microarray slide in the presence of labeled Universal Mouse Reference RNA (UMRR, Stratagene, LaJolla, CA). A total of 24 RNA samples were used in this analysis. Briefly, five hundred nanograms of total RNA were used for gene expression profiling following reverse transcription and T-7 polymerase-mediated amplification/labeling with Cyanine-5 CTP. Labeled subject cRNA was co-hybridized to Agilent G4112F Whole Mouse Genome 4x44K oligonucleotide arrays with equimolar amounts of Cyanine-3 labeled UHRR. Slides were hybridized, washed, and scanned on an Axon 4000b microarray scanner. The data were processed using Feature Extaction software (Agilent, Santa Clara, CA).