Conserved themes in target recognition by the PAH1 and PAH2 domains of the Sin3 transcriptional corepressor
Conserved themes in target recognition by the PAH1 and PAH2 domains of the Sin3 transcriptional corepressor
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DOI：
10.1016/j.jmb.2007.11.079
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发表时间：
2008-02-01
影响因子：
5.6
通讯作者：
Radhakrishnan, Ishwar
中科院分区：
文献类型：
--
作者：
Sahu, Sarata C.;Swanson, Kurt A.;Radhakrishnan, Ishwar
转录因子将染色质修饰辅调节因子复合物募集到基因组的特定位点是许多真核生物转录调控途径中的重要步骤。组蛋白去乙酰化酶相关的Sin3辅阻遏物复合物通过与Sin3的N-末端PAH结构域直接相互作用被大量不同的转录因子招募。在这里，我们描述的解决方案的mSin3A PAH1结构域的载脂蛋白形式，当绑定到SAP 25，辅阻遏复合物的一个组成部分。与apo-mSin3A PAH 2结构域不同，apo-PAH 1结构域是构象纯的，并且大部分但不完全折叠。mSin3A PAH 1和SAP 25的相互作用片段的一部分在复合物形成时发生折叠。SAP 25通过两亲性螺旋结合到PAH 1表面上的主要疏水性裂缝。值得注意的是，与NRSF（一种与SAP 25无关的转录因子）结合mSin3B PAH 1结构域时所采用的螺旋方向相比，螺旋方向发生了逆转。螺旋方向的逆转与潜在的PAH1相互作用基序的逆转相关，这与先前描述的mSin3A PAH2结构域的主题相呼应。这些所谓的I型和11型PAH1相互作用基序的定义，使我们能够预测这些基序在以前的实验表征的PAHI粘合剂的精确位置。最后，我们探讨了涉及PAH 1和PAH 2结构域的蛋白质-蛋白质相互作用的特异性决定因素。这些研究表明，即使用等价的PAH 1残基保守替换PAH 2残基也足以显著改变这些蛋白质-蛋白质相互作用的亲和力和特异性。(C)2007爱思唯尔有限公司保留所有权利。
The recruitment of chromatin-modifying coregulator complexes by transcription factors to specific sites of the genome constitutes an important step in many eukaryotic transcriptional regulatory pathways. The histone deacetylase-associated Sin3 corepressor complex is recruited by a large and diverse array of transcription factors through direct interactions with the N-terminal PAH domains of Sin3. Here, we describe the solution structures of the mSin3A PAH1 domain in the apo form and when bound to SAP25, a component of the corepressor complex. Unlike the apo-mSin3A PAH2 domain, the apo-PAH1 domain is conformationally pure and is largely, but not completely, folded. Portions of the interacting segments of both mSin3A PAH1 and SAP25 undergo folding upon complex formation. SAP25 binds through an amphipathic helix to a predominantly hydrophobic cleft on the surface of PAH1. Remarkably, the orientation of the helix is reversed compared to that adopted by NRSF, a transcription factor unrelated to SAP25, upon binding to the mSin3B PAH1 domain. The reversal in helical orientations is correlated with a reversal in the underlying PAH1-interaction motifs, echoing a theme previously described for the mSin3A PAH2 domain. The definition of these so-called type I and type 11 PAH1-interaction motifs has allowed us to predict the precise location of these motifs within previously experimentally characterized PAHI binders. Finally, we explore the specificity determinants of protein-protein interactions involving the PAH1 and PAH2 domains. These studies reveal that even conservative replacements of PAH2 residues with equivalent PAH1 residues are sufficient to alter the affinity and specificity of these protein-protein interactions dramatically. (C) 2007 Elsevier Ltd. All rights reserved.