Hypersensitive termination of the hypoxic response by a disordered protein switch

Area of Science:

• Molecular Biology
• Cellular Signaling
• Protein-Protein Interactions

Background:

• Cellular response to hypoxia is crucial for survival and adaptation.
• Hypoxia-Inducible Factor 1 alpha (HIF-1α) regulates adaptive genes via TAZ1 domain of CBP/p300.
• CITED2 acts as a negative feedback regulator by competing for TAZ1 binding.

Purpose of the Study:

• To elucidate the molecular mechanism by which CITED2 displaces HIF-1α from TAZ1.
• To understand how CITED2 activates the negative feedback circuit controlling hypoxic response.

Main Methods:

• Investigated the interaction between CITED2, HIF-1α, and TAZ1.
• Characterized the role of the conserved LP(Q/E)L motif in TAZ1 binding and displacement.
• Utilized studies on intrinsically disordered proteins to explain the regulatory switch.

Main Results:

• Human CITED2 displaces HIF-1α by forming a transient ternary complex with TAZ1.
• CITED2's LPEL motif competes for the same binding site, inducing a conformational change in TAZ1.
• This conformational change allosterically enhances HIF-1α dissociation, activating a rapid negative feedback loop.

Conclusions:

• CITED2 activates a highly responsive negative feedback circuit to attenuate the hypoxic response.
• The hypersensitive regulation relies on the unique properties of intrinsically disordered proteins.
• This mechanism likely represents a common cellular strategy for rapid environmental signal response.