Suchergebnisse

Hypoxia inducible factor (HIF) up-regulates the transcription of a few hundred genes required for the adaptation to hypoxia. This restricted set of targets is in sharp contrast with the widespread distribution of the HIF binding motif throughout the genome. Here, we investigated the transcriptional response of GYS1 and RUVBL2 genes to hypoxia to understand the mechanisms that restrict HIF activity toward specific genes. GYS1 and RUVBL2 genes are encoded by opposite DNA strands and separated by a short intergenic region (∼1kb) that contains a functional hypoxia response element equidistant to both genes. However, hypoxia induced the expression of GYS1 gene only. Analysis of the transcriptional response of chimeric constructs derived from the intergenic region revealed an inhibitory sequence whose deletion allowed RUVBL2 induction by HIF. Enhancer blocking assays, performed in cell culture and transgenic zebrafish, confirmed the existence of an insulator element within this inhibitory region that could explain the differential regulation of GYS1 and RUVBL2 by hypoxia. Hence, in this model, the selective response to HIF is achieved with the aid of insulator elements. This is the first report suggesting a role for insulators in the regulation of differential gene expression in response to environmental signals ; The Ministerio de Ciencia e Innovación (Spanish Ministry of Science and Innovation, MICINN) grant numbers Nucleic Acids Research, 2012, Vol. 40, No. 5 1925 SAF2008-03147 (to L.del P.), BIO2009-1297 (to L.M.), BFU2010-14839 (to J.L.G.-S.), CSD2007-00008 (to J.L.G.-S.); Comunidad Autónoma de Madrid grant number S-SAL-0311_2006 (to L.del P.); the 7th Research Framework Programme of the European Union grant number METOXIA project ref. HEALTH-F2-2009-222741 (to L.del P.); Junta de Andalucía grant number CVI-3488 (to J.L.G.-S.); CIBERER (ISCIII) (to E.M.). Funding for open access charge: SAF2008-03147 (to L.del P.)

The transcriptional response driven by Hypoxia-inducible factor (HIF) is central to the adaptation to oxygen restriction. Despite recent characterization of genome-wide HIF DNA binding locations and hypoxia-regulated transcripts in different cell types, the molecular bases of HIF target selection remain unresolved. Herein, we combined multi-level experimental data and computational predictions to identify sequence motifs that may contribute to HIF target selectivity. We obtained a core set of bona fide HIF binding regions by integrating multiple HIF1 DNA binding and hypoxia expression profiling datasets. This core set exhibits evolutionarily conserved binding regions and is enriched in functional responses to hypoxia. Computational prediction of enriched transcription factor binding sites identified sequence motifs corresponding to several stress-responsive transcription factors, such as activator protein 1 (AP1), cAMP response element-binding (CREB), or CCAAT-enhancer binding protein (CEBP). Experimental validations on HIF-regulated promoters suggest a functional role of the identified motifs in modulating HIF-mediated transcription. Accordingly, transcriptional targets of these factors are over-represented in a sorted list of hypoxia-regulated genes. Altogether, our results implicate cooperativity among stress-responsive transcription factors in fine-tuning the HIF transcriptional response ; This work was supported by Ministerio de Ciencia e Innovación (Spanish Ministry of Science and Innovation, MICINN) [grant number SAF2008-03147 to L. del P.], Comunidad Autónoma de Madrid [grant number S-SAL-0311_2006 to L. del P.] and the 7th Research Framework Programme of the European Union [grant number METOXIA project ref. HEALTH-F2-2009-222741] to L. del P. D.V. was a recipient of PhD funding from the Spanish Ministry of Science and Innovation [FPU programme] and the European Molecular Biology Organization [Short-Term Fellowships]

Deregulated protein and Ca2+ homeostasis underlie synaptic dysfunction and neurodegeneration in Huntington disease (HD); however, the factors that disrupt homeostasis are not fully understood. Here, we determined that expression of downstream regulatory element antagonist modulator (DREAM), a multifunctional Ca2+-binding protein, is reduced in murine in vivo and in vitro HD models and in HD patients. DREAM downregulation was observed early after birth and was associated with endogenous neuroprotection. In the R6/2 mouse HD model, induced DREAM haplodeficiency or blockade of DREAM activity by chronic administration of the drug repaglinide delayed onset of motor dysfunction, reduced striatal atrophy, and prolonged life span. DREAM-related neuroprotection was linked to an interaction between DREAM and the unfolded protein response (UPR) sensor activating transcription factor 6 (ATF6). Repaglinide blocked this interaction and enhanced ATF6 processing and nuclear accumulation of transcriptionally active ATF6, improving prosurvival UPR function in striatal neurons. Together, our results identify a role for DREAM silencing in the activation of ATF6 signaling, which promotes early neuroprotection in HD ; This work was funded by the Instituto de Salud Carlos III/CIBERNED (to J.R. Naranjo, B. Mellström, and A. Rábano), FISS-RIC RD12/0042/0019 (to C. Valenzuela), Madrid regional government/Neurodegmodels (to J.R. Naranjo), MINECO grants SAF2010-21784 and SAF2014-53412-R (to J.R. Naranjo), SAF2012-32209 (to M. Gutierrez-Rodriguez), SAF2010-14916 and SAF2013-45800-R (to C. Valenzuela), and a grant from the Swedish Research Council (J.Y. Li)