title: Mechanism of CREB recognition and coactivation by the CREB-regulated transcriptional coactivator CRTC2.
abstract: Basic leucine zipper (bZip) transcription factors regulate cellular gene expression in response to a variety of extracellular signals and nutrient cues. Although the bZip domain is widely known to play significant roles in DNA binding and dimerization, recent studies point to an additional role for this motif in the recruitment of the transcriptional apparatus. For example, the cAMP response element binding protein (CREB)-regulated transcriptional coactivator (CRTC) family of transcriptional coactivators has been proposed to promote the expression of calcium and cAMP responsive genes, by binding to the CREB bZip in response to extracellular signals. Here we show that the CREB-binding domain (CBD) of CRTC2 folds into a single isolated 28-residue helix that seems to be critical for its interaction with the CREB bZip. The interaction is of micromolar affinity on palindromic and variant half-site cAMP response elements (CREs). The CBD and CREB assemble on the CRE with 2:2:1 stoichiometry, consistent with the presence of one CRTC binding site on each CREB monomer. Indeed, the CBD helix and the solvent-exposed residues in the dimeric CREB bZip coiled-coil form an extended protein-protein interface. Because mutation of relevant bZip residues in this interface disrupts the CRTC interaction without affecting DNA binding, our results illustrate that distinct DNA binding and transactivation functions are encoded within the structural constraints of a canonical bZip domain.
authors.affiliation: Department of Molecular Biosciences, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Qianyi
authors.initials: Q
authors.lastname: Luo
authors.forename: Kristin
authors.initials: K
authors.lastname: Viste
authors.forename: Janny Concha
authors.initials: JC
authors.lastname: Urday-Zaa
authors.forename: Ganesan
authors.initials: G
authors.lastname: Senthil Kumar
authors.forename: Wen-Wei
authors.initials: WW
authors.lastname: Tsai
authors.forename: Afsaneh
authors.initials: A
authors.lastname: Talai
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Mayo
authors.forename: Marc
authors.initials: M
authors.lastname: Montminy
authors.forename: Ishwar
authors.initials: I
authors.lastname: Radhakrishnan
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D017124:Conserved Sequence; D018360:Crystallography, X-Ray / Q000379:methods; D000242:Cyclic AMP / Q000737:chemistry; D017362:Cyclic AMP Response Element-Binding Protein / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004247:DNA / Q000737:chemistry; D004305:Dose-Response Relationship, Drug; D005786:Gene Expression Regulation; D057809:HEK293 Cells; D006801:Humans; D016350:Leucine Zippers; D008969:Molecular Sequence Data; D009154:Mutation; D011485:Protein Binding; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary; D017386:Sequence Homology, Amino Acid; D015398:Signal Transduction; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
chemical_list: C493245:CRTC2 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D014157:Transcription Factors; D004247:DNA; D000242:Cyclic AMP; D003545:Cysteine