Mechanism of CREB recognition and coactivation by the CREB-regulated transcriptional coactivator CRTC2
Mechanism of CREB recognition and coactivation by the CREB-regulated transcriptional coactivator CRTC2
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DOI：
10.1073/pnas.1219028109
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发表时间：
2012-12-18
影响因子：
11.1
通讯作者：
Radhakrishnan, Ishwar
中科院分区：
文献类型：
--
作者：
Luo, Qianyi;Viste, Kristin;Radhakrishnan, Ishwar
碱性亮氨酸拉链(BZip)转录因子调节细胞基因表达，以响应各种细胞外信号和营养信号。虽然众所周知，bZip结构域在DNA结合和二聚化过程中发挥着重要作用，但最近的研究表明，该基序在转录装置的招募中还发挥了额外的作用。例如，cAMP反应元件结合蛋白(CREB)调节的转录共激活因子(CRTC)家族转录共激活物已被提出，通过与CREB bZip结合来响应细胞外信号，促进钙和cAMP反应基因的表达。在这里，我们证明了CRTC2的CREB结合结构域(CBD)折叠成一个单独的28个残基的螺旋，这似乎是它与CREB bZip相互作用的关键。回文cAMP反应元件和变异cAMP反应元件上的相互作用具有微摩尔亲和力。CBD和CREB以2：2：1的化学计量比组装在CRE上，与每个CREB单体上存在一个CRTC结合位点一致。事实上，CBD螺旋和二聚体CREB bZip卷曲线圈中暴露于溶剂中的残基形成了一个延伸的蛋白质-蛋白质界面。由于该界面上相关bZip残基的突变破坏了CRTC的相互作用，而不影响DNA结合，我们的结果表明，不同的DNA结合和反式激活功能是在规范的bZip结构域的结构限制内编码的。
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.