Project description:As a critical cellular stress sensor, p53 mediates a variety of defensive processes including cell-cycle arrest, apoptosis, and senescence to prevent propagation of hyperproliferative cells or cells with a damaged genome, hence the formation of neoplasia. Transactivation of downstream genes plays an important while sometimes controversial role in regulating these cellular processes. To evaluate the dependence on transcriptional activation in p53’s activities, we generated genetically-modified mouse lines carrying mutations in the transactivation domains (TADs) of p53. These transactivatio-deficient mutants serve as unique reagents to probe the dependence on robust transactivation in p53-mediated cellular functions, as well as the underneath mechanisms. To identify genes differentially regulated by these p53 mutants, we performed gene expression profiling analysis on mouse embryonic fibroblast cells (MEFs) from these mice in the context of oncogenic Ras-induced premature cellular senescence. Mouse embryonic fibroblasts (MEFs) with different p53 genotypes were infected with retroviral H-Ras V12, which induces premature cellular senescence in p53 wild-type MEFs but not in p53 null MEFs. 5 genotypic groups of MEFs were used in the study: (i) p53L25Q/W26S, or "25,26", in which the first TAD (transactivation domain) of p53 is disrupted by the mutation, 5 biological samples; (ii) p53W53Q/F54S, or "53,54", in which the second TAD of p53 is disrupted by the mutation, 3 biological samples; (iii) p53L25Q/W26S/W53Q/F54S, or "QM", in which both TADs or p53 are disrupted, 3 biological samples; (iv) p53 wild-type, or "WT", 6 biological samples; (v) p53 null, or "Null", 6 biological samples.
Project description:As a critical cellular stress sensor, p53 mediates a variety of defensive processes including cell-cycle arrest, apoptosis, and senescence to prevent propagation of hyperproliferative cells or cells with a damaged genome, hence the formation of neoplasia. Transactivation of downstream genes plays an important while sometimes controversial role in regulating these cellular processes. To evaluate the dependence on transcriptional activation in p53’s activities, we generated genetically-modified mouse lines carrying mutations in the transactivation domains (TADs) of p53. These transactivatio-deficient mutants serve as unique reagents to probe the dependence on robust transactivation in p53-mediated cellular functions, as well as the underneath mechanisms. To identify genes differentially regulated by these p53 mutants, we performed gene expression profiling analysis on mouse embryonic fibroblast cells (MEFs) from these mice in the context of oncogenic Ras-induced premature cellular senescence.
Project description:Acute Pten loss initiates prostate tumorigenesis characterized by cellular senescence response. Here we examine the cellular senescence response in epithelial individual cells, by single-cell RNA sequencing (scRNAseq) in Ptenpc-/- and Ptenpc-/-; Timp1-/- GEMMs. ScRNAseq analysis determines a cluster of senescent cells expressing the senescence-related genes. A significant positive correlation is observed between the senescence score and Bcl2 expression. This provides the rational for targeting senescent cells using Bcl2 inhibitor.
Project description:Ectopic expression of the transcription factors Oct4, Sox2, Klf4 and c-Myc (OSKM) can reprogram somatic cells into induced pluripotent stem cells (iPSCs). These iPSCs are highly similar to embryonic stem cells and can be used for regenerative medicine, drug screening and disease modelling. Despite recent advances, reprogramming is a slow and inefficient process. This suggests that there are several safeguarding mechanisms to counteract cell fate conversion. Cellular senescence is one of these barriers, which is mediated through activation of the tumour suppressors p53/p21CIP1, p15INK4b and p16INK4a. In this study, we have screened for shRNAs blunting reprogramming-induced senescence. We found that mTOR depletion bypasses OSKM-indced senescence but not RAS-induced senescence. To investigate the differences between the two types of senescence, we performed RNA-sequencing (RNA-Seq). Cells were transduced with OSKM or RAS expression and treated with 2 doses of the mTOR inhibitor Rapaycin for 10 days.
Project description:Mis-sense mutations affecting TP53 promote carcinogenesis both by inactivating its tumor suppressive functions, and by conferring aberrant pro-carcinogenic activities. We report here that mis-sense mutants in the p53 DNA-binding domain (DBD) and the transactivation domain (TAD) unexpectedly activate pro-carcinogenic epidermal growth factor receptor (EGFR) signaling via distinct, previously unrecognized molecular mechanisms. DBD- and TAD-specific TP53 mutants exhibited different cellular localization patterns and induced distinct gene expression profiles. Combining mass spectrometry with drug compound screens, we identified EGFR as a major signaling factor that is stabilized by TAD and DBD mutants in the cytosolic and nuclear compartments respectively, in a tissue-independent manner. Mechanistically, TAD mutants promote EGFR-mediated signaling by enhancing EGFR interaction with AKT via DDX31 in the cytosol. Conversely, DBD mutants maintain EGFR activity in the nucleus, by blocking EGFR interaction with the phosphatase SHP1, triggering upregulation of c-Myc and Cyclin D1 levels. Therapeutically, the sensitivity of DBD mutants to EGFR inhibition is enhanced by increasing the affinity of EGFR for SHP1, while that of TAD mutants can be induced by concurrent inhibition of AKT, mTOR or PI3K signaling. Thus, our findings suggest that gain-of-function, mis-sense mutations affecting two different p53 domains promote carcinogenesis by enhancing EGFR signaling via distinctive mechanisms. Our findings imply that cancer cells bearing domain-specific mutations may have distinct and exploitable therapeutic vulnerabilities.