Nucleus-vacuole junctions in Saccharomyces cerevisiae are formed through the direct interaction of Vac8p with Nvj1p
Nucleus-vacuole junctions in Saccharomyces cerevisiae are formed through the direct interaction of Vac8p with Nvj1p
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DOI：
10.1091/mbc.11.7.2445
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发表时间：
2000-07-01
影响因子：
3.3
通讯作者：
Goldfarb, DS
中科院分区：
文献类型：
--
作者：
Pan, XZ;Roberts, P;Goldfarb, DS
Vac8p是一种液泡膜蛋白，是高效液泡遗传和融合、细胞质-液泡靶向和孢子形成所必需的。通过类比其他犰狳结构域蛋白，包括β -连环蛋白和输入蛋白，我们假设Vac8p在液泡膜上连接了各种因子。双杂化和共固化实验表明，Vac8p确实与多个结合伙伴形成复合物，包括Apg13p、Vab2p和Nvj1p。在这里，我们描述了Vac8p-Nvj1p复合物在核-液泡（NV）连接形成中的惊人作用。Nvj1p是一个完整的核膜蛋白，通过其c端40-60个氨基酸（aa）与细胞质溶胶中的Vac8p相互作用。Nvj1p绿色荧光蛋白（GFP）集中在细胞核与一个或多个液泡密切接触部位的小斑块或筏状物中。先前我们发现Vac8p-GFP集中在液泡间筏中，这可能促进液泡-液泡融合，以及液泡簇边缘的“孤儿”筏中。Vac8p红色筛选的GFP （YFP）孤儿筏与Nvj1p蓝色筛选的GFP （CFP）共定位于NV连接位点。gfp标记的核孔复合物（NPCs）被排除在NV连接处。在vac8-Delta细胞中，Nvj1p-GFP通常不能浓缩成筏状，而是包围细胞核。nvj1-Delta和vac8-Delta细胞均无NV连接。Nvj1p的过表达引起NV连接的深度增殖。我们得出结论，Vac8p和Nvj1p是一个新的细胞器间连接装置的必要组成部分。
Vac8p is a vacuolar membrane protein that is required for efficient vacuole inheritance and fusion, cytosol-to-vacuole targeting, and sporulation. By analogy to other armadillo domain proteins, including beta-catenin and importin alpha, we hypothesize that Vac8p docks various factors at the vacuole membrane. Two-hybrid and copurfication assays demonstrated that Vac8p does form complexes with multiple binding partners, including Apg13p, Vab2p, and Nvj1p. Here we describe the surprising role of Vac8p-Nvj1p complexes in the formation of nucleus-vacuole (NV) junctions. Nvj1p is an integral membrane protein of the nuclear envelope and interacts with Vac8p in the cytosol through its C-terminal 40-60 amino acids (aa). Nvj1p green fluorescent protein (GFP) concentrated in small patches or rafts at sites of close contact between the nucleus and one or more vacuoles. Previously we showed that Vac8p-GFP concentrated in intervacuole rafts, where is it likely to facilitate vacuole-vacuole fusion, and in "orphan" rafts at the edges of vacuole clusters. Orphan rafts of Vac8p red-sifted GFP (YFP) colocalize at sites of NV junctions with Nvj1p blue-sifted GFP (CFP). GFP-tagged nuclear pore complexes (NPCs) were excluded from NV junctions. In vac8-Delta cells, Nvj1p-GFP generally failed to concentrate into rafts and, instead, encircled the nucleus. NV junctions were absent in both nvj1-Delta and vac8-Delta cells. Overexpression of Nvj1p caused the profound proliferation of NV junctions. We conclude that Vac8p and Nvj1p are necessary components of a novel interorganelle junction apparatus.