Hypoxia-inducible factor 2-alpha (HIF-2α) C-terminal transactivation domain (C-TAD) (HIF-2α C-TAD)

The Hypoxia-inducible factor 2-alpha (HIF-2α) C-terminal transactivation domain (C-TAD) is a specialized functional region of the HIF-2α protein, which is encoded by the EPAS1 gene [UniProt: Q99814]. This domain plays a pivotal role in the adaptive response to low oxygen levels by recruiting transcriptional co-activators such as p300 and CREB-binding protein (CBP) to the hypoxia-response elements (HREs) of target genes [PubMed: 11566883]. The activity of the C-TAD is post-translationally regulated by the Factor Inhibiting HIF-1 (FIH-1), which hydroxylates the Asn847 residue under normoxic conditions, thereby blocking the interaction with p300/CBP [PubMed: 12150925]. In diseases such as clear cell renal cell carcinoma (ccRCC), the loss of the von Hippel-Lindau (VHL) protein leads to the stabilization and constitutive activity of HIF-2α, driving oncogenic processes like angiogenesis and erythropoiesis [PubMed: 28104771]. While clinical inhibitors like Belzutifan target the PAS-B domain to prevent HIF-2α/HIF-1β dimerization, the C-TAD remains a key structural component for the protein's transactivation potential and a subject of interest for developing inhibitors that disrupt co-activator recruitment [PubMed: 34385158]. Therapeutic targeting of the HIF-2α pathway, particularly in VHL-deficient cancers, has been validated by the approval of Belzutifan, though specific small-molecule inhibitors of the C-TAD/p300 interaction are currently in the experimental stage [FDA: Welireg, PubMed: 15314656].

Other names

EPAS1 C-TADHIF2A C-TADEndothelial PAS domain-containing protein 1 C-terminal transactivation domainHIF-2-alpha C-terminal activation domainHIF-2α C-TAD

The primary mechanism of action for clinical HIF-2α inhibitors, such as Belzutifan, involves binding to the PAS-B domain of the protein, which triggers a conformational change that disrupts its dimerization with HIF-1β (ARNT), thereby preventing the formation of a functional transcription factor complex [PubMed: 27595565]. Experimental strategies specifically targeting the C-terminal transactivation domain (C-TAD) focus on inhibiting the recruitment of co-activators like p300/CBP, which is necessary for the transcriptional activation of hypoxia-responsive genes [PubMed: 15314656]. Additionally, the activity of the C-TAD is naturally modulated by the Factor Inhibiting HIF-1 (FIH-1), which hydroxylates a conserved asparagine residue (Asn847) under normoxic conditions to prevent co-activator binding [PubMed: 12150925].