RESUMO
We have earlier shown that p53-FL and its translational isoform ∆40p53 are differentially regulated. In this study, we have investigated the cellular effect of ∆40p53 regulation on downstream gene expression, specifically miRNAs. Interestingly, ∆40p53 showed antagonistic regulation of miR-186-5p as compared to either p53 alone or a combination of both the isoforms. We have elucidated the miR-186-5p mediated effect of ∆40p53 in cell proliferation. Upon expression of ∆40p53, we observed a significant decrease in YY1 levels, an established target of miR-186-5p, which is involved in cell proliferation. Further assays with anti-miR-186 established the interdependence of ∆40p53- miR-186-5p-YY1- cell proliferation. The results unravel a new dimension toward the understanding of ∆40p53 functions, which seems to regulate cellular fate independent of p53FL.
Assuntos
Proliferação de Células/fisiologia , MicroRNAs/genética , MicroRNAs/metabolismo , Proteína Supressora de Tumor p53/genética , Proteína Supressora de Tumor p53/metabolismo , Fator de Transcrição YY1/genética , Fator de Transcrição YY1/metabolismo , Células HCT116 , Humanos , Luciferases de Vaga-Lume , Isoformas de Proteínas/genética , Isoformas de Proteínas/metabolismo , Fator de Transcrição YY1/antagonistas & inibidoresRESUMO
p53 and its translational isoform Δ40p53 are involved in many important cellular functions like cell cycle, cell proliferation, differentiation and metabolism. Expression of both the isoforms can be regulated at different steps. In this study, we explored the role of 3'UTR in regulating the expression of these two translational isoforms. We report that the trans acting factor, Polypyrimidine Tract Binding protein (PTB), also interacts specifically with 3'UTR of p53 mRNA and positively regulates expression of p53 isoforms. Our results suggest that there is interplay between miRNAs and PTB at the 3'UTR under normal and stress conditions like DNA damage. Interestingly, PTB showed some overlapping binding regions in the p53 3'UTR with miR-1285. In fact, knockdown of miR-1285 as well as expression of p53 3'UTR with mutated miR-1285 binding sites resulted in enhanced association of PTB with the 3'UTR, which provides mechanistic insights of this interplay. Taken together, the results provide a plausible molecular basis of how the interplay between miRNAs and the PTB protein at the 3'UTR can play pivotal role in fine tuning the expression of the two p53 isoforms.
Assuntos
Regiões 3' não Traduzidas/genética , Genes p53 , MicroRNAs/metabolismo , Proteína de Ligação a Regiões Ricas em Polipirimidinas/metabolismo , RNA Mensageiro/metabolismo , Proteína Supressora de Tumor p53/biossíntese , Células A549 , Sítios de Ligação , Linhagem Celular , Regulação da Expressão Gênica , Humanos , Imunoprecipitação , MicroRNAs/antagonistas & inibidores , MicroRNAs/genética , Conformação de Ácido Nucleico , Polimorfismo de Nucleotídeo Único , Ligação Proteica , Isoformas de Proteínas/biossíntese , Isoformas de Proteínas/genética , Interferência de RNA , RNA Interferente Pequeno/genéticaRESUMO
p53 is a well known tumor suppressor protein that plays a critical role in cell cycle arrest and apoptosis. It has several isoforms which are produced by transcriptional and posttranscriptional regulatory mechanisms. p53 mRNA has been demonstrated to be translated into two isoforms, full-length p53 (FL-p53) and a truncated isoform ΔN-p53 by the use of alternative translation initiation sites. The mechanism of translation regulation of these two isoforms was further elucidated by the discovery of IRES elements in the p53 mRNA. These two IRESs were shown to regulate the translation of p53 and ΔN-p53 in a distinct cell-cycle phase-dependent manner. This review focuses on the current understanding of the regulation of p53 IRES mediated translation and the role of cis and trans acting factors that influence expression of p53 isoforms.
