RESUMEN
MicroRNA-138 (miR-138) is a pro-survival oncomiR for glioma stem cells. In malignant gliomas, dysregulated expression of microRNAs, such as miR-138, promotes Tumour initiation and progression. Here, we identify the ancillary role of the CCAAT/enhancer binding protein ß (C/EBPß) as a transcriptional activator of miR-138. We demonstrate that a short 158 bp DNA sequence encoding the precursor of miR-138-2 is essential and sufficient for transcription of miR-138. This short sequence includes the A-box and B-box elements characteristic of RNA Polymerase III (Pol III) promoters, and is also directly bound by C/EBPß via an embedded 'C/EBPß responsive element' (CRE). CRE and the Pol III B-box element overlap, suggesting that C/EBPß and transcription factor 3C (TFIIIC) interact at the miR-138-2 locus. We propose that this interaction is essential for the recruitment of the RNA Pol III initiation complex and associated transcription of the oncomiR, miR-138 in malignant gliomas.
Asunto(s)
Proteína beta Potenciadora de Unión a CCAAT/genética , Glioma/genética , MicroARNs/genética , ARN Polimerasa III/metabolismo , Transcripción Genética , Animales , Proteína beta Potenciadora de Unión a CCAAT/metabolismo , Línea Celular Tumoral , Regulación Neoplásica de la Expresión Génica , Glioma/metabolismo , Glioma/terapia , Células HEK293 , Humanos , Subunidad gamma Común de Receptores de Interleucina/deficiencia , Subunidad gamma Común de Receptores de Interleucina/genética , Ratones Endogámicos NOD , Ratones Noqueados , Ratones SCID , Oncogenes/genética , Unión Proteica , Interferencia de ARN , Tratamiento con ARN de Interferencia/métodos , Ensayos Antitumor por Modelo de Xenoinjerto/métodosRESUMEN
Epithelial carcinomas are well known to activate a prolonged wound-healing program that promotes malignant transformation. Wound closure requires the activation of keratinocyte migration via a dual-state molecular switch. This switch involves production of either the anti-migratory microRNA miR-198 or the pro-migratory follistatin-like 1 (FSTL1) protein from a single transcript; miR-198 expression in healthy skin is down-regulated in favor of FSTL1 upon wounding, which enhances keratinocyte migration and promotes re-epithelialization. Here, we reveal a defective molecular switch in head and neck squamous cell carcinoma (HNSCC). This defect shuts off miR-198 expression in favor of sustained FSTL1 translation, driving metastasis through dual parallel pathways involving DIAPH1 and FSTL1. DIAPH1, a miR-198 target, enhances directional migration through sequestration of Arpin, a competitive inhibitor of Arp2/3 complex. FSTL1 blocks Wnt7a-mediated repression of extracellular signal-regulated kinase phosphorylation, enabling production of MMP9, which degrades the extracellular matrix and facilitates metastasis. The prognostic significance of the FSTL1-DIAPH1 gene pair makes it an attractive target for therapeutic intervention.
