Complex regulation of the transactivation function of hypoxia-inducible factor-1 alpha by direct interaction with two distinct domains of the CREB-binding protein/p300.

Activation of transcription in response to low oxygen tension is mediated by the hypoxia-inducible factor-1 (HIF-1). HIF-1 is a heterodimer of two proteins: aryl hydrocarbon receptor nuclear translocator and the oxygen-regulated HIF-1 alpha. The C-terminal activation domain of HIF-1 alpha has been shown to interact with cysteine/histidine-rich region 1 (CH1) ...
of the coactivator CBP/p300 in a hypoxia-dependent manner. However, HIF forms lacking C-terminal activation domain (naturally occurring or genetically engineered) are still able to activate transcription of target genes in hypoxia. Here, we demonstrate that the N-terminal activation domain (N-TAD) of HIF-1 alpha interacts with endogenous CBP and that this interaction facilitates its transactivation function. Our results show that interaction of HIF-1 alpha N-TAD with CBP/p300 is mediated by the CH3 region of CBP known to interact with, among other factors, p53. Using fluorescence resonance energy transfer experiments, we demonstrate that N-TAD interacts with CH3 in vivo. Coimmunoprecipitation assays using endogenous proteins showed that immunoprecipitation of CBP in hypoxia results in the recovery of a larger fraction of HIF-1 alpha than of p53. Chromatin immunoprecipitation demonstrated that at 1% O(2) CBP is recruited to a HIF-1 alpha but not to a p53 target gene. Upon activation of both pathways, lower levels of chromatin-associated CBP were detected at either target gene promoter. These results identify CBP as the coactivator directly interacting with HIF-1 alpha N-TAD and mediating the transactivation function of this domain. Thus, we suggest that in hypoxia HIF-1 alpha is a major CBP-interacting transcription factor that may compete with other CBP-dependent factors, including p53, for limiting amounts of this coactivator, underscoring the complexity in the regulation of gene expression by HIF-1 alpha.
Mesh Terms:
2,2'-Dipyridyl, Anoxia, Cell Line, Chelating Agents, Cysteine, E1A-Associated p300 Protein, HeLa Cells, Histidine, Humans, Hypoxia-Inducible Factor 1, alpha Subunit, Kidney, Mutagenesis, Protein Interaction Domains and Motifs, Protein Structure, Tertiary, Transcriptional Activation, Tumor Suppressor Protein p53, p300-CBP Transcription Factors
J. Biol. Chem.
Date: Jan. 22, 2010
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