title: An E2F/miR-20a autoregulatory feedback loop.
abstract: The E2F family of transcription factors is essential in the regulation of the cell cycle and apoptosis. While the activity of E2F1-3 is tightly controlled by the retinoblastoma family of proteins, the expression of these factors is also regulated at the level of transcription, post-translational modifications and protein stability. Recently, a new level of regulation of E2Fs has been identified, where micro-RNAs (miRNAs) from the mir-17-92 cluster influence the translation of the E2F1 mRNA. We now report that miR-20a, a member of the mir-17-92 cluster, modulates the translation of the E2F2 and E2F3 mRNAs via binding sites in their 3'-untranslated region. We also found that the endogenous E2F1, E2F2, and E2F3 directly bind the promoter of the mir-17-92 cluster activating its transcription, suggesting an autoregulatory feedback loop between E2F factors and miRNAs from the mir-17-92 cluster. Our data also point toward an anti-apoptotic role for miR-20a, since overexpression of this miRNA decreased apoptosis in a prostate cancer cell line, while inhibition of miR-20a by an antisense oligonucleotide resulted in increased cell death after doxorubicin treatment. This anti-apoptotic role of miR-20a may explain some of the oncogenic capacities of the mir-17-92 cluster. Altogether, these results suggest that the autoregulation between E2F1-3 and miR-20a is important for preventing an abnormal accumulation of E2F1-3 and may play a role in the regulation of cellular proliferation and apoptosis.
authors.affiliation: Département de Biochimie, Université de Montréal, Montréal, Quebec H3C 3J7, Canada.
authors.forename: Yannick
authors.initials: Y
authors.lastname: Sylvestre
authors.forename: Vincent
authors.initials: V
authors.lastname: De Guire
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Querido
authors.forename: Utpal K
authors.initials: UK
authors.lastname: Mukhopadhyay
authors.forename: Véronique
authors.initials: V
authors.lastname: Bourdeau
authors.forename: François
authors.initials: F
authors.lastname: Major
authors.forename: Gerardo
authors.initials: G
authors.lastname: Ferbeyre
authors.forename: Pascal
authors.initials: P
authors.lastname: Chartrand
mesh_terms: D016923:Cell Death / Q000187:drug effects / Q000235:genetics; D045744:Cell Line, Tumor; D004317:Doxorubicin / Q000494:pharmacology; D050684:E2F Transcription Factors / Q000235:genetics / Q000378:metabolism*; D025461:Feedback, Physiological; D006801:Humans; D035683:MicroRNAs / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008956:Models, Chemical; D016376:Oligonucleotides, Antisense; D011401:Promoter Regions, Genetic; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation
chemical_list: D050684:E2F Transcription Factors; D035683:MicroRNAs; D016376:Oligonucleotides, Antisense; D012333:RNA, Messenger; D004317:Doxorubicin