The mitotic regulator survivin binds as a monomer to its functional interactor borealin
The mitotic regulator survivin binds as a monomer to its functional interactor borealin
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DOI：
10.1074/jbc.m706233200
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发表时间：
2007-11-30
影响因子：
4.8
通讯作者：
Cochran, Andrea G.
中科院分区：
文献类型：
--
作者：
Bourhis, Eric;Hymowitz, Sarah G.;Cochran, Andrea G.
Survivin是IAP (（i)棒状下抑制(a)棒状下凋亡）蛋白家族的成员，部分由锌结合杆状病毒抑制重复（BIR）结构域的存在而定义。大多数BIR结构域结合以丙氨酸开头的短序列，通过这种方式，它们识别并阻断凋亡途径中关键靶点的作用。然而，Survivin与典型IAP配体的结合非常弱。Survivin的独特特征是BIR结构域后面的长c端螺旋和介导Survivin同二聚化的短片段（连接螺旋和BIR结构域）。尽管对Survivin本身的结构有了详细的了解，但目前对Survivin如何识别细胞结合伴侣缺乏了解，因此，关于Survivin功能的许多问题仍未得到解答。我们确定了Survivin的两种共晶结构和染色体乘客蛋白Borealin的最小结合片段，Borealin是一种经过验证的功能相互作用物。Survivin和Borealin之间的相互作用涉及Survivin的长c端螺旋和Borealin长螺旋之间的广泛填充。令人惊讶的是，在Survivin同型二聚化界面和Borealin的一小段之间发生了另一个重要的相互作用。这个片段在结构上模仿和取代了一个Survivin单体。这种意想不到的相互作用的相关性是通过诱变两个关键的Borealin残基来测试的。引入HeLa细胞的突变体Borealin在有丝分裂过程中无法正确定位，也导致其他染色体乘客蛋白定位错误。这表明突变体是显性阴性的，并证实了在晶体结构中鉴定的相互作用表面的功能重要性。
Survivin is a member of the IAP ( (i) under bar nhibitor of (a) under bar poptosis) protein family, defined in part by the presence of a zinc-binding baculoviral inhibitory repeat (BIR) domain. Most BIR domains bind short sequences beginning with alanine, and in this manner, they recognize and block the action of key targets in apoptotic pathways. However, Survivin binds only very weakly to typical IAP ligands. Unique features of Survivin are the long C-terminal helix following the BIR domain and a short segment ( linking the helix and BIR domains) that mediates Survivin homodimerization. Despite this detailed knowledge of the structure of Survivin itself, there is a current lack of understanding about how Survivin recognizes cellular binding partners, and consequently, many questions about Survivin function remain unanswered. We determined two co-crystal structures of Survivin and a minimal binding fragment from the chromosomal passenger protein Borealin, a well validated functional interactor. The interaction between Survivin and Borealin involves extensive packing between the long C-terminal helix of Survivin and a long Borealin helix. Surprisingly, an additional important interaction occurs between the Survivin homodimerization interface and a short segment of Borealin. This segment both structurally mimics and displaces one Survivin monomer. The relevance of this unexpected interaction was tested by mutagenesis of two key Borealin residues. Mutant Borealin introduced into HeLa cells failed to localize properly during mitosis and also caused mislocalization of other chromosomal passenger proteins. This suggests that the mutant is dominant-negative and confirms the functional importance of the interaction surface identified in the crystal structures.