Functional dissection of a transcriptionally active, target-specific Hox-Pbx complex
Functional dissection of a transcriptionally active, target-specific Hox-Pbx complex
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DOI：
10.1093/emboj/16.12.3644
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发表时间：
1997-06-16
期刊：
影响因子：
11.4
通讯作者：
Zappavigna, V
中科院分区：
文献类型：
--
作者：
DiRocco, G;Mavilio, F;Zappavigna, V
Hox 基因控制细胞命运并指定脊椎动物发育中的区域特征，Hox 蛋白在体外表现出宽松的 DNA 结合选择性，表明功能特异性是通过转录辅助因子的作用在体内实现的，基于遗传和生化证据，Pbx 蛋白是发挥这种作用的良好候选者。我们报告说，人类 Pbx1 和 HOXB1 蛋白可以通过遗传特征的 Hox 靶标协同激活转录，即指导小鼠 Hoxb-1 基因 (b1-ARE) 在发育中的后脑中空间限制表达的自动调节元件。在 b1-ARE 上，只有 HOX 蛋白的有限子集（HOSA1、HOXB1、HOXA2）能够与 Pbx1 协同结合并激活转录。 b1-ARE 的选择性识别是由 HOX 同源结构域的 N 端区域介导的。 HOXB1 和 Pbs1 的 DNA 结合和蛋白质-蛋白质相互作用功能对于在 b1-ARE 上组装转录活性复合物都是必需的。该复合物的功能解剖允许将主要激活结构域定位在 HOXB1 N 端区域中，并在 Pbx1a 中包含的 Pbx1 C 端区域中定位另外一个激活结构域，但不包含在选择性剪接的 Pbx1b 同种型中。我们的结果表明，Pbx1 作为 Hox 蛋白的转录辅助因子，允许选择性识别和协同激活调节因子靶序列。
Hox genes control cell fates and specify regional identities in vertebrate development, Hox proteins show a relaxed DNA-binding selectivity in vitro, suggesting that functional specificity is achieved in vivo through the action of transcriptional co-factors, Pbx proteins are good candidates for such a role, on the basis of both genetic and biochemical evidence. We report that the human Pbx1 and HOXB1 proteins can cooperatively activate transcription through a genetically characterized Hox target, i.e. an autoregulatory element directing spatially restricted expression of the murine Hoxb-1 gene (b1-ARE) in the developing hindbrain. On the b1-ARE, only a restricted subset of HOX proteins (HOSA1, HOXB1, HOXA2) are able to bind cooperatively with Pbx1 and activate transcription. Selective recognition of the b1-ARE is mediated by the N-terminal region of the HOX Homeodomain. The DNA-binding and protein-protein interaction functions of HOXB1 and Pbs1 are all necessary for the assembly of a transcriptionally active complex on the b1-ARE. Functional dissection of the complex allowed the localization of the main activation domain in the HOXB1 N-terminal region, and of an additional one in the C-terminal region of Pbx1 contained in the Pbx1a but not in the alternatively spliced Pbx1b isoform. Our results indicate that Pbx1 acts Its a transcriptional co-factor of Hox proteins, allowing selective recognition and cooperative activation of regulators target sequences.