Structure of HoxA9 and Pbx1 bound to DNA: Hox hexapeptide and DNA recognition anterior to posterior
Structure of HoxA9 and Pbx1 bound to DNA: Hox hexapeptide and DNA recognition anterior to posterior
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DOI：
10.1101/gad.1103303
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发表时间：
2003-08-15
影响因子：
10.5
通讯作者：
Wolberger, C
中科院分区：
文献类型：
--
作者：
LaRonde-LeBlanc, NA;Wolberger, C
同源域蛋白的 HOX/HOM 超家族通过所有后生动物中保守的机制控制细胞命运和节段胚胎模式。 Hox 基因在染色体上的线性排列与 HOX 蛋白表达沿胚胎前后轴的空间分布相关。大多数 HOX 蛋白与 TALE 型同源域蛋白 PBC 家族的成员（包括人类 Pbx1）协同结合 DNA。 HOX 和 PBC 蛋白之间的协同 DNA 结合需要 HOX 同源结构域的 N 端残基，称为六肽，其在前调节 HOX 蛋白和后调节 HOX 蛋白之间的序列显着不同。我们在此报告了与 Pbx1 和 DNA 复合的后 HOX 蛋白 HoxA9 的 1.9 埃分辨率结构，这表明与之前确定的前 HOX/PBC 结构相比，后 Hox 六肽采用了改变的构象。该结构中额外的非特异性相互作用和改变的 DNA 构象导致了与前 HOX 蛋白相比，后 HOX 蛋白具有更强的 DNA 结合亲和力和改变的特异性。野生型和突变型 HoxA9 和 HoxB1 的 DNA 结合研究表明，同源域 N 端臂中的残基对于正确的 DNA 序列识别至关重要，尽管这些残基与 DNA 碱基缺乏直接接触。这些结果有助于阐明 HOX 蛋白的转录调控机制，并展示 DNA 结合蛋白如何利用间接接触来确定序列特异性。
The HOX/HOM superfamily of homeodomain proteins controls cell fate and segmental embryonic patterning by a mechanism that is conserved in all metazoans. The linear arrangement of the Hox genes on the chromosome correlates with the spatial distribution of HOX protein expression along the anterior-posterior axis of the embryo. Most HOX proteins bind DNA cooperatively with members of the PBC family of TALE-type homeodomain proteins, which includes human Pbx1. Cooperative DNA binding between HOX and PBC proteins requires a residue N-terminal to the HOX homeodomain termed the hexapeptide, which differs significantly in sequence between anterior- and posterior-regulating HOX proteins. We report here the 1.9-Angstrom-resolution structure of a posterior HOX protein, HoxA9, complexed with Pbx1 and DNA, which reveals that the posterior Hox hexapeptide adopts an altered conformation as compared with that seen in previously determined anterior HOX/PBC structures. The additional nonspecific interactions and altered DNA conformation in this structure account for the stronger DNA-binding affinity and altered specificity observed for posterior HOX proteins when compared with anterior HOX proteins. DNA-binding studies of wild-type and mutant HoxA9 and HoxB1 show residues in the N-terminal arm of the homeodomains are critical for proper DNA sequence recognition despite lack of direct contact by these residues to the DNA bases. These results help shed light on the mechanism of transcriptional regulation by HOX proteins and show how DNA-binding proteins may use indirect contacts to determine sequence specificity.