Structural integration in hypoxia-inducible factors.

Area of Science:

• Biochemistry
• Molecular Biology
• Structural Biology

Background:

• Hypoxia-inducible factors (HIFs) are critical regulators of cellular responses to low oxygen.
• HIFs control genes involved in erythropoiesis, angiogenesis, and metabolism, processes vital for tumor growth and progression.
• HIFs are attractive anticancer targets due to their role in tumorigenesis.

Purpose of the Study:

• To elucidate the structural basis of HIF-α-ARNT heterodimer function.
• To identify potential small-molecule binding sites on HIF heterodimers for targeted cancer therapy.
• To understand the structural mechanisms of hypoxia response element (HRE) recognition.

Main Methods:

• X-ray crystallography was used to determine the structures of mouse HIF-2α-ARNT and HIF-1α-ARNT heterodimers.
• Structures were solved in complex with small molecules and DNA (hypoxia response elements).
• Analysis of quaternary architecture, small-molecule binding pockets, and DNA-binding interfaces.

Main Results:

• Detailed crystal structures of HIF-2α-ARNT and HIF-1α-ARNT heterodimers were obtained.
• A conserved quaternary architecture was observed, with ARNT spiraling around HIF-α subunits.
• Five distinct small-molecule binding pockets were identified, including PAS domain sites and an interfacial cavity.
• The DNA-binding head and distal PAS domain cooperate for efficient hypoxia response element recognition.
• Cancer-associated HIF-α mutations were mapped to functionally critical regions affecting DNA binding and domain stability.

Conclusions:

• The structural data provide a mechanistic understanding of HIF heterodimer assembly and function.
• Identified small-molecule binding sites offer opportunities for developing novel HIF-targeted anticancer drugs.
• Understanding HIF-DNA interactions is crucial for designing inhibitors that disrupt oncogenic transcriptional programs.