A previously unidentified amino-terminal domain regulates transcriptional activity of wild-type and disease-associated human GLI2
A previously unidentified amino-terminal domain regulates transcriptional activity of wild-type and disease-associated human GLI2
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DOI：
10.1093/hmg/ddi222
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发表时间：
2005-08-01
影响因子：
3.5
通讯作者：
Muenke, M
中科院分区：
文献类型：
--
作者：
Roessler, E;Ermilov, AN;Muenke, M
含锌指的Gli蛋白介导对Hedgehog(HH)信号的应答，Gli2在小鼠的这一途径中起主要的转录激活作用。疾病相关突变的发现也表明GLI2在人类HH信号中也发挥了关键作用。在这里，我们发现人类GLI2含有先前未描述的5‘序列，将氨基末端延伸出额外的328个氨基酸。在体外，全长GLI2的转录活性比GLI2 Delta N(以前被认为代表整个GLI2蛋白)低30倍，这表明全长蛋白中存在一个氨基末端抑制域。GLI2 Delta N在体内也显示出强大的转录活性：在小鼠皮肤中过表达导致形成类似于基底细胞癌的HH非依赖性上皮下生长，在人类中与结构性HH信号有关。这个额外的、功能相关的GLI2序列的发现使我们重新检查了几个致病的人类GLI2突变体，现在包含整个氨基末端结构域。根据突变影响的功能域，突变的GLI2蛋白表现出功能丧失或显性负活性。此外，氨基端的缺失取消了突变体GLI2的显性负活性，表明该结构域是病原性GLI2转录抑制活性所必需的。我们的结果证实了氨基末端转录抑制域的存在，该结构域在调节野生型GLI2的功能方面发挥着关键作用，并且对于与人类疾病相关的GLI2突变体的显性负活性是必不可少的。
Zinc finger-containing Gli proteins mediate responsiveness to Hedgehog (Hh) signaling, with Gli2 acting as the major transcriptional activator in this pathway in mice. The discovery of disease-associated mutations points to a critical role for GLI2 in human Hh signaling as well. Here, we show that human GLI2 contains previously undescribed 5' sequence, extending the amino-terminus an additional 328 amino acids. In vitro, transcriptional activity of full-length GLI2 is up to 30 times lower than that of GLI2 Delta N (previously thought to represent the entire GLI2 protein), revealing the presence of an amino-terminal repressor domain in the full-length protein. GLI2 Delta N also exhibits potent transcriptional activity in vivo: overexpression in mouse skin leads to the formation of Hh-independent epithelial downgrowths resembling basal cell carcinomas, which in humans are associated with constitutive Hh signaling. The discovery of this additional, functionally relevant GLI2 sequence led us to re-examine several pathogenic human GLI2 mutants, now containing the entire amino-terminal domain. On the basis of the functional domains affected by the mutations, mutant GLI2 proteins exhibited either loss-of-function or dominant-negative activity. Moreover, deletion of the amino-terminus abrogated dominant-negative activity of mutant GLI2, revealing that this domain is required for transcriptional repressor activity of pathogenic GLI2. Our results establish the presence of an amino-terminal transcriptional repressor domain that plays a critical role in modulating the function of wild-type GLI2 and is essential for dominant-negative activity of a GLI2 mutant associated with human disease.