Interaction of the TAZ1 domain of the CREB-binding protein with the activation domain of CITED2: regulation by competition between intrinsically unstructured ligands for non-identical binding sites.
The TAZ1 domain of the homologous transcriptional coactivators CREB-binding protein (CBP) and p300 forms a complex with CITED2 (CBP/p300-interacting transactivator with ED-rich tail), inhibiting the activity of the hypoxia inducible factor (HIF-1alpha) and thereby attenuating the cellular response to low tissue oxygen concentration. We report the NMR structure of the CBP TAZ1 domain bound to the activation domain of CIT-ED2. The structure of TAZ1, consisting of four alpha-helices (alpha(1)-alpha(4)) stabilized by three zinc atoms, is very similar in the CITED2 and HIF-1alpha complexes. The activation domain of CITED2 is unstructured when free and folds upon binding, forming a helix (termed alpha(A)) and an extended structure that wraps around TAZ1. The CITED2 alpha(A) helix packs in the TAZ1 alpha(1)/alpha(4) interface, a site that forms weak interactions with the poorly defined aminoterminal alpha-helix of HIF-1alpha. CITED2 and HIF-1alpha both contain a four residue motif, LP(E/Q)L, which binds in the TAZ1 alpha(1)/alpha(2)/alpha(3) junction in each complex. The carboxyl-terminal region of CITED2 forms an extended structure with hydrophobic contacts in the TAZ1 alpha(1)/alpha(3) interface in the site occupied by the HIF-1alpha alpha(B) helix. CITED2 does not bind at all to the TAZ1 site occupied by the HIF-1alpha carboxyl-terminal helix. The HIF-1alpha and CITED2 domains utilize partly overlapping surfaces of TAZ1 to achieve high affinity binding and to compete effectively with each other for interaction with CBP/p300; CITED2 and HIF-1alpha use these binding sites differently to maintain similar binding affinities in order to displace each other in a feedback loop during the hypoxic response.
De Guzman
Roberto N
RN
Department of Molecular Biology and Skaggs Institute for Chemical Biology, The Scripps Research Institute, La Jolla, California 92037, USA.
Martinez-Yamout
Maria A
MA
Dyson
H Jane
HJ
Wright
Peter E
PE
D000595:Amino Acid Sequence; D000818:Animals; D001665:Binding Sites; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000378:metabolism*; D006801:Humans; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000737:chemistry / Q000378:metabolism*; D011485:Protein Binding; D011487:Protein Conformation; D017434:Protein Structure, Tertiary; D012097:Repressor Proteins / Q000737:chemistry / Q000378:metabolism*; D016415:Sequence Alignment; D015534:Trans-Activators / Q000737:chemistry / Q000378:metabolism*; D014157:Transcription Factors
C486381:CITED2 protein, human; C110087:Cited2 protein, mouse; D004268:DNA-Binding Proteins; C497442:HIF1A protein, human; C497443:Hif1a protein, mouse; D051793:Hypoxia-Inducible Factor 1; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D008024:Ligands; D009687:Nuclear Proteins; D012097:Repressor Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050882:CREB-Binding Protein; C494363:CREBBP protein, human; C494364:Crebbp protein, mouse