Department of Molecular Genetics, The Ohio State University, Columbus, OH 43210, USA.
J Cell Biol. 2012 Jan 23;196(2):203-11. doi: 10.1083/jcb.201108098.
Inner nuclear membrane Sad1/UNC-84 (SUN) proteins interact with outer nuclear membrane (ONM) Klarsicht/ANC-1/Syne homology (KASH) proteins, forming linkers of nucleoskeleton to cytoskeleton conserved from yeast to human and involved in positioning of nuclei and chromosomes. Defects in SUN-KASH bridges are linked to muscular dystrophy, progeria, and cancer. SUN proteins were recently identified in plants, but their ONM KASH partners are unknown. Arabidopsis WPP domain-interacting proteins (AtWIPs) are plant-specific ONM proteins that redundantly anchor Arabidopsis RanGTPase-activating protein 1 (AtRanGAP1) to the nuclear envelope (NE). In this paper, we report that AtWIPs are plant-specific KASH proteins interacting with Arabidopsis SUN proteins (AtSUNs). The interaction is required for both AtWIP1 and AtRanGAP1 NE localization. AtWIPs and AtSUNs are necessary for maintaining the elongated nuclear shape of Arabidopsis epidermal cells. Together, our data identify the first KASH members in the plant kingdom and provide a novel function of SUN-KASH complexes, suggesting that a functionally diverged SUN-KASH bridge is conserved beyond the opisthokonts.
核内层膜 Sad1/UNC-84（SUN）蛋白与核外层膜（ONM）Klarsicht/ANC-1/Syne 同源（KASH）蛋白相互作用，形成从酵母到人保守的核骨架到细胞骨架的连接体，参与核和染色体的定位。SUN-KASH 桥的缺陷与肌肉营养不良、早衰和癌症有关。SUN 蛋白最近在植物中被发现，但它们的 ONM KASH 伴侣尚不清楚。拟南芥 WPP 结构域相互作用蛋白（AtWIPs）是植物特异性的 ONM 蛋白，可将拟南芥 RanGTP 酶激活蛋白 1（AtRanGAP1）冗余地锚定到核膜（NE）。在本文中，我们报告 AtWIPs 是与拟南芥 SUN 蛋白（AtSUNs）相互作用的植物特异性 KASH 蛋白。这种相互作用是 AtWIP1 和 AtRanGAP1 NE 定位所必需的。AtWIPs 和 AtSUNs 对于维持拟南芥表皮细胞的长形核形状是必要的。总之，我们的数据鉴定了植物王国中的第一个 KASH 成员，并提供了 SUN-KASH 复合物的新功能，表明功能分化的 SUN-KASH 桥在后生动物之外是保守的。
