Insulin-like growth factor binding protein-6 (IGFBP-6) interacts with DNA-end binding protein Ku80 to regulate cell fate
Insulin-like growth factor binding protein-6 (IGFBP-6) interacts with DNA-end binding protein Ku80 to regulate cell fate
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DOI：
10.1016/j.cellsig.2010.02.006
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发表时间：
2010-07-01
影响因子：
4.8
通讯作者：
Han, Victor K.
中科院分区：
文献类型：
--
作者：
Iosef, Cristiana;Vilk, Gregory;Han, Victor K.
胰岛素样生长因子结合蛋白-6(IGFBP-6)是一种生长抑制蛋白，调节胰岛素样生长因子(IGF)的可获得性。我们最近报道了IGFBP-6通过其转位到细胞核而在细胞内发挥作用。我们现在证明IGFBP-6通过与参与DNA稳定和修复的核蛋白(如Ku80、Ku70、组蛋白H2B和Importin-α)串联亲和力来协同纯化。此外，这份报告表明IGFBP-6和Ku80通过IGFBP-6中Ku80的两个活性结合位点特异性地相互作用。其中一个结合位点[196RKR199]，作为IGFBP-6中NLS序列的一部分，也与Importin-α结合，后者可能选择性地与Ku80竞争，调节其向细胞核的运输。此外，IGFBP-6基于细胞周期模式与Ku80共定位。IGFBP-6的过表达增加了有丝分裂细胞中的核Ku80，并降低了有丝分裂后的Ku80。已知，如果IGFBP-6高表达诱导细胞凋亡，在我们的模型中，特定siRNAs下调Ku80的表达增强了IGFBP-6过表达引起的细胞凋亡效应。这项研究表明，IGFBP-6通过潜在地调节Ku80在DNA修复过程中的可用性来改变细胞的存活。这一作用代表了IGFBP-6等生长抑制蛋白调节细胞命运的新机制。(C)2010 Elsevier Inc.保留所有权利。
Insulin-like growth factor binding protein-6 (IGFBP-6) is a growth inhibitory protein that regulates the availability of insulin-like growth factors (IGFs). We recently reported that IGFBP-6 exerts intracellular actions via its translocation to the nucleus. We now show that IGFBP-6 co-purifies by tandem-affinity with nuclear proteins involved in DNA stability and repair such as Ku80, Ku70, histone H2B and importin-alpha. Furthermore, this report shows that IGFBP-6 and Ku80 interact specifically using two active binding sites for Ku80 in IGFBP-6. One of the binding sites [196RKR199], as part of the NLS-sequence in IGFBP-6 also binds importin-alpha which may selectively compete with Ku80 regulating its trafficking to the nucleus. Moreover, IGFBP-6 co-localized with Ku80 based on a cell cycle pattern. Overexpression of IGFBP-6 increased the nuclear Ku80 in mitotic cells and reduced it post-mitosis. It is known that if highly expressed IGFBP-6 induces apoptosis and in our model, the down-regulation of Ku80 by specific siRNAs enhanced the apoptotic effect caused by the IGFBP-6 overexpression. This study demonstrates that IGFBP-6 alters cell survival by potentially regulating the availability of Ku80 for the DNA-repair process. This action represents a novel mechanism by which growth inhibitory proteins such as IGFBP-6 regulate cell fate. (C) 2010 Elsevier Inc. All rights reserved.