Redox-Regulated Recruitment of the Transcriptional Coactivators CREB-Binding Protein and SRC-1 to Hypoxia-Inducible Factor 1α

Abstract

Hypoxia-inducible factor 1α (HIF-1α) functions as a transcription factor that is activated by decreased cellular oxygen concentrations to induce expression of a network of genes involved in angiogenesis, erythropoiesis, and glucose homeostasis. Here we demonstrate that two members of the SRC-1/p160 family of transcriptional coactivators harboring histone acetyltransferase activity, SRC-1 and transcription intermediary factor 2 (TIF2), are able to interact with HIF-1α and enhance its transactivation potential in a hypoxia-dependent manner. HIF-1α contains within its C terminus two transactivation domains. The hypoxia-inducible activity of both these domains was enhanced by either SRC-1 or the CREB-binding protein (CBP)/p300 coactivator. Moreover, at limiting concentrations, SRC-1 produced this effect in synergy with CBP. Interestingly, this effect was strongly potentiated by the redox regulatory protein Ref-1, a dual-function protein harboring DNA repair endonuclease and cysteine reducing activities. These data indicate that all three proteins, CBP, SRC-1, and Ref-1, are important components of the hypoxia signaling pathway and have a common function in regulation of HIF-1α function in hypoxic cells. Given the absence of cysteine residues in one of the Ref-1-regulated transactivation domains of HIF-1α, it is thus possible that Ref-1 functions in hypoxic cells by targeting critical steps in the recruitment of the CBP–SRC-1 coactivator complex.

ACKNOWLEDGMENTS

We thank M. G. Parker for the SRC-1 M1234 construct. We also thank Anders Berkenstam and Yuichi Makino for stimulating discussions and helpful advice.

This study was supported by grants from the Swedish Medical Research Council, Pharmacia and Upjohn, Akiyama Foundation, and NOVARTIS Foundation (Japan) for the Promotion of Science.