SUN-1 and ZYG-12, Mediators of Centrosome-Nucleus Attachment, Are a Functional SUN/KASH Pair in Caenorhabditis elegans
SUN-1 and ZYG-12, Mediators of Centrosome-Nucleus Attachment, Are a Functional SUN/KASH Pair in Caenorhabditis elegans
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DOI：
10.1091/mbc.e08-10-1034
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发表时间：
2009-11-01
影响因子：
3.3
通讯作者：
Malone, Christian J.
中科院分区：
文献类型：
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作者：
Minn, I. L.;Rolls, Melissa M.;Malone, Christian J.
Klarsicht/ ac -1/Syne/homology (KASH)/Sad-1/UNC-84 （SUN）蛋白对可以作为细胞器和核骨架之间的连接物。秀丽隐杆线虫ZYG-12和SUN-1是中心体-核附着所必需的。虽然SUN-1具有典型的SUN结构域，但ZYG-12具有发散的KASH结构域。在这里，我们确定了ZYG-12迷你KASH结构域是功能性的，并且与部分线圈结构域结合，足以实现核膜定位。假设ZYG-12和SUN-1分别是核膜外蛋白和核膜内蛋白，并相互作用，但没有直接研究它们的拓扑结构和物理相互作用。我们发现ZYG-12是II型外核膜蛋白，SUN-1是II型内核膜蛋白。这些蛋白质通过ZYG-12迷你KASH结构域和SUN-1的一个不包括SUN结构域的区域在核膜的腔内空间相互作用。假设SUN-1将ZYG-12限制在ONM，阻止其通过内质网扩散。我们通过光漂白后的荧光恢复证实了ZYG-12在ONM处确实是不动的，并且表明SUN-1足以在细胞中定位ZYG-12。这项工作支持当前的KASH/SUN对模型，并突出了定义KASH域的序列元素的多样性。
Klarsicht/ANC-1/Syne/homology (KASH)/Sad-1/UNC-84 (SUN) protein pairs can act as connectors between cytoplasmic organelles and the nucleoskeleton. Caenorhabditis elegans ZYG-12 and SUN-1 are essential for centrosome-nucleus attachment. Although SUN-1 has a canonical SUN domain, ZYG-12 has a divergent KASH domain. Here, we establish that the ZYG-12 mini KASH domain is functional and, in combination with a portion of coiled-coil domain, is sufficient for nuclear envelope localization. ZYG-12 and SUN-1 are hypothesized to be outer and inner nuclear membrane proteins, respectively, and to interact, but neither their topologies nor their physical interaction has been directly investigated. We show that ZYG-12 is a type II outer nuclear membrane (ONM) protein and that SUN-1 is a type II inner nuclear membrane protein. The proteins interact in the luminal space of the nuclear envelope via the ZYG-12 mini KASH domain and a region of SUN-1 that does not include the SUN domain. SUN-1 is hypothesized to restrict ZYG-12 to the ONM, preventing diffusion through the endoplasmic reticulum. We establish that ZYG-12 is indeed immobile at the ONM by using fluorescence recovery after photobleaching and show that SUN-1 is sufficient to localize ZYG-12 in cells. This work supports current models of KASH/SUN pairs and highlights the diversity in sequence elements defining KASH domains.