Characterization of two distinct subfamilies of SUN-domain proteins in Arabidopsis and their interactions with the novel KASH-domain protein AtTIK
Characterization of two distinct subfamilies of SUN-domain proteins in Arabidopsis and their interactions with the novel KASH-domain protein AtTIK
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DOI：
10.1093/jxb/eru368
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发表时间：
2014-12-01
影响因子：
6.9
通讯作者：
Tatout, Christophe
中科院分区：
文献类型：
--
作者：
Graumann, Katja;Vanrobays, Emmanuel;Tatout, Christophe
SUN结构域蛋白属于一个基因家族，包括经典的Cter-SUN和mid-SUN亚家族，其通过蛋白质内SUN结构域的位置来区分。虽然存在于动物和植物物种中，但到目前为止，中SUN蛋白质的描述仍然很少。在这里，我们使用了遗传学，酵母双杂交和植物瞬时表达方法的组合，以更好地表征SUN家族在拟南芥。首先，我们验证了中SUN蛋白亚家族作为一个单系组从酵母到植物保守。拟南芥Cter-SUN（AtSUN 1和AtSUN 2）和mid-SUN（AtSUN 3和AtSUN 4）蛋白表达为荧光蛋白融合体，是膜相关的并且定位于核膜（NE）和内质网。然而，只有Cter-Sun亚家族在NE处富集。我们研究了两个亚家族成员之间的相互作用，并确定了介导相互作用所必需的卷曲螺旋结构域。在突变体植物中进一步证实了mid-SUN亚家族的功能意义，其对早期种子发育至关重要，并参与核形态学。最后，我们证明了这两个亚家族与AtWIP 1的KASH结构域相互作用，并确定了一个新的根特异性KASH结构域蛋白AtTIK。AtTIK定位于NE并影响核形态。我们的研究表明，拟南芥Cter-SUN和mid-SUN蛋白参与了一个复杂的蛋白质网络在核膜上，让人想起在其他王国中发现的核骨架和细胞骨架（LINC）复合体的链接。
SUN-domain proteins belong to a gene family including classical Cter-SUN and mid-SUN subfamilies differentiated by the position of the SUN domain within the protein. Although present in animal and plant species, mid-SUN proteins have so far remained poorly described. Here, we used a combination of genetics, yeast two-hybrid and in planta transient expression methods to better characterize the SUN family in Arabidopsis thaliana. First, we validated the mid-SUN protein subfamily as a monophyletic group conserved from yeast to plant. Arabidopsis Cter-SUN (AtSUN1 and AtSUN2) and mid-SUN (AtSUN3 and AtSUN4) proteins expressed as fluorescent protein fusions are membrane-associated and localize to the nuclear envelope (NE) and endoplasmic reticulum. However, only the Cter-SUN subfamily is enriched at the NE. We investigated interactions in and between members of the two subfamilies and identified the coiled-coil domain as necessary for mediating interactions. The functional significance of the mid-SUN subfamily was further confirmed in mutant plants as essential for early seed development and involved in nuclear morphology. Finally, we demonstrated that both subfamilies interact with the KASH domain of AtWIP1 and identified a new root-specific KASH-domain protein, AtTIK. AtTIK localizes to the NE and affects nuclear morphology. Our study indicates that Arabidopsis Cter-SUN and mid-SUN proteins are involved in a complex protein network at the nuclear membranes, reminiscent of the LInker of Nucleoskeleton and Cytoskeleton (LINC) complex found in other kingdoms.