RESUMEN
Regulation of vascular endothelial growth factor (VEGF) expression is a complex process involving a plethora of transcriptional regulators. The AP-1 transcription factor is considered as facilitator of hypoxia-induced VEGF expression through interaction with hypoxia-inducible factor (HIF) which plays a major role in mediating the cellular hypoxia response. As yet, both the decisive AP-1 subunit leading to VEGF induction and the molecular mechanism by which this subunit is activated have not been deciphered. Here, we demonstrate that the AP-1 subunit junB is a target gene of hypoxia-induced signaling via NF-kappaB. Loss of JunB in various cell types results in severely impaired hypoxia-induced VEGF expression, although HIF is present and becomes stabilized. Thus, we identify JunB as a critical independent regulator of VEGF transcription and provide a mechanistic explanation for the inherent vascular phenotypes seen in JunB-deficient embryos, ex vivo allantois explants and in vitro differentiated embryoid bodies. In support of these findings, tumor angiogenesis was impaired in junB(-/-) teratocarcinomas because of severely impaired paracrine-acting VEGF and the subsequent inability to efficiently recruit host-derived vessels.
Asunto(s)
Regulación de la Expresión Génica/fisiología , FN-kappa B/metabolismo , Neoplasias/irrigación sanguínea , Neovascularización Patológica/fisiopatología , Proteínas Proto-Oncogénicas c-jun/metabolismo , Factor A de Crecimiento Endotelial Vascular/metabolismo , Alantoides/citología , Alantoides/metabolismo , Animales , Hipoxia de la Célula/fisiología , Línea Celular Tumoral , Células Cultivadas , Inmunoprecipitación de Cromatina , Ensayo de Cambio de Movilidad Electroforética , Técnica del Anticuerpo Fluorescente , Immunoblotting , Ratones , Ratones Transgénicos , Neovascularización Patológica/metabolismo , Reacción en Cadena de la Polimerasa de Transcriptasa InversaRESUMEN
The molecular mechanism triggering the organization of endothelial cells (ECs) in multicellular tubules is mechanistically still poorly understood. We demonstrate that cell-autonomous endothelial functions of the AP-1 subunit JunB are required for proper endothelial morphogenesis both in vivo in mouse embryos with endothelial-specific ablation of JunB and in in vitro angiogenesis models. By cDNA microarray analysis, we identified core-binding factor beta (CBFbeta), which together with the Runx proteins forms the heterodimeric core-binding transcription complex CBF, as a novel JunB target gene. In line with our findings, expression of the CBF target MMP-13 was impaired in JunB-deficient ECs. Reintroduction of CBFbeta into JunB-deficient ECs rescued the tube formation defect and MMP-13 expression, indicating an important role for CBFbeta in EC morphogenesis.