c-Jun and Hypoxia-Inducible Factor 1 Functionally Cooperate in Hypoxia-Induced Gene Transcription

Abstract

Under low-oxygen conditions, cells develop an adaptive program that leads to the induction of several genes, which are transcriptionally regulated by hypoxia-inducible factor 1 (HIF-1). On the other hand, there are other factors which modulate the HIF-1-mediated induction of some genes by binding to cis-acting motifs present in their promoters. Here, we show that c-Jun functionally cooperates with HIF-1 transcriptional activity in different cell types. Interestingly, a dominant-negative mutant of c-Jun which lacks its transactivation domain partially inhibits HIF-1-mediated transcription. This cooperative effect is not due to an increase in the nuclear amount of the HIF-1α subunit, nor does it require direct binding of c-Jun to DNA. c-Jun and HIF-1α are able to associate in vivo but not in vitro, suggesting that this interaction involves the participation of additional proteins and/or a posttranslational modification of these factors. In this context, hypoxia induces phosphorylation of c-Jun at Ser⁶³ in endothelial cells. This process is involved in its cooperative effect, since specific blockade of the JNK pathway and mutation of c-Jun at Ser⁶³ and Ser⁷³ impair its functional cooperation with HIF-1. The functional interplay between c-Jun and HIF-1 provides a novel insight into the regulation of some genes, such as the one for VEGF, which is a key regulator of tumor angiogenesis.

We thank E. Huang and R. Davis for their generous gifts of HIF-1 expression vectors and GST constructs; we also thank P. Angel, R. Pope, and M. Karin for kindly providing us their c-Jun plasmids and A. Israel, M. Rincón, P. Muñoz, and G. R. Crabtree for their p 75 BFLuc, 2XAP1Luc, pcDNA3-Flag-JBD (JIP1), and pSH107c plasmids, respectively. We are very grateful to L. del Peso, R. Ramos, J. M. Redondo, M. López-Cabrera, F. Sánchez-Madrid, and M. C. Castellanos for their critical reading of the manuscript.

This work was supported by grants from the Ministerio de Educación y Cultura (PM 98/0024), from Fondo de Investigaciones Sanitarias (Fis 98/1382), and from Comunidad Autónoma de Madrid (CAM 08.3/0022/00). A.A. and F.V. were supported by fellowships from the Ministerio de Educación y Cultura; M.D.G. and J.A. were supported by fellowships from Comunidad Autónoma de Madrid.