Analysis of gene expression in p53-null cell types following deletion of Mdm2
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE98705 | GEO | 2017/09/06
SECONDARY ACCESSION(S): PRJNA385963
REPOSITORIES: GEO
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Project description:Adult cardiomyocytes (CM) are terminally differentiated cells with minimal regenerative capacity, making cardiac tissue particularly vulnerable to injury. Thus, defining the roadblocks responsible for adult CM cell cycle arrest lies at the core of developing therapies to regenerate myocyte loss following injurious events such as myocardial infarction. We have previously shown that inactivating the p53/Mdm2 tumor suppressor circuitry, specifically in the heart (using the Cre-loxP recombination system of bacteriophage P1), can allow differentiated CMs to regain proliferative capacity, through an upregulation of factors involved in cell cycle re-entry. These factors are repressed in quiescent CMs, in part through the action of microRNAs (miRNAs). Notably, knockout of either p53 or Mdm2 individually was insufficient to promote CM proliferation. Therefore, we hypothesized that inactivation of p53/Mdm2-regulated miRNAs could promote the expression of cell cycle activators and induce proliferation of adult murine CMs. To identify miRNAs regulated by both p53 and Mdm2, total miRNA expression profiles from cardiac specific p53/Mdm2 double knockout (DKO) mouse hearts were compared with those from cardiac-specific single knockouts (p53KO and Mdm2KO), and vehicle-injected controls using the Nanostring nCounter mouse miRNA expression assay. This revealed a profile of 11 significantly downregulated miRNAs in the proliferative DKO hearts (versus vehicle-injected control), that were enriched for mRNA targets involved in cell cycle regulation. In vitro studies have demonstrated that knockdown of these 11 miRNAs in neonatal rat cardiomyocytes can increase the occurrence of cytokinetic events. Ultimately, we aim to inject antagomirs targeting these miRNAs into animals post-myocardial infarction to determine the effect of p53/Mdm2-regulated miRNAs on heart function and CM proliferation in vivo.
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Project description:The p53 family is known as a family of transcription factors with functions in tumor suppression and development. Whereas the central DNA binding domain is highly conserved among the three family members p53, p63 and p73, the C-terminal domains (CTDs) are diverse and subject to alternative splicing and post-translational modification. Here we demonstrate that the CTDs strongly influence DNA binding and transcriptional activity. While p53 and the p73 isoform p73ï§ have basic CTDs and form weak sequence-specific protein-DNA complexes, the major p73 isoforms ï¡, ï¢ and ï¤ have neutral CTDs and bind DNA strongly. A basic CTD has been previously shown to enable sliding along the DNA backbone and to facilitate the search for binding sites in the complex genome. Our experiments, however, reveal that a basic CTD also reduces protein-DNA complex stability, intranuclear mobility, promoter occupancy in vivo, transgene activation and induction of cell cycle arrest or apoptosis. A basic CTD in p53 and p73ï§ therefore provides both positive and negative regulatory functions presumably to enable rapid switching of protein activity in response to stress. In contrast, most p73 isoforms exhibit constitutive DNA binding activity consistent with a predominant role in developmental control. Experiment Overall Design: Infection of H1299 cell with different p73/p53 constructs by adenoviral system
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