THE ROLE OF THE NUCLEAR ENVELOPE IN INTRACELLULAR PROTEIN SORTING

蛋白质的正确区室化 细胞核可能在调节细胞生长中起作用， 发展 含有氨基酸的合成肽 负责SV 40核定位的序列 大T抗原和存在于细胞质中的修饰序列 变体已被用于研究蛋白质输入细胞核。 这些合成肽已被用于产生多克隆抗体。 和特异性结合细胞核的单克隆抗体 定位序列 这种短肽，当化学上 与大荧光蛋白β-藻红蛋白偶联， 特异性地将蛋白质缀合物靶向细胞核。 这种结合物穿过核膜的运输是 在微感染到培养细胞中或在 使用大鼠肝细胞核的体外输入测定。 运输是时间， 温度和能量依赖性;只有含有 定位序列被正确地传输。 核孔 复合物穿过核被膜，可以介导 进入细胞核。 我们已经证明了外层核 膜是膜糖蛋白的重要部位 合成. 我们还证明了携带 细胞质定向的O-连接的GlcNAc是 核孔复合体 核孔糖蛋白可以是 用凝集素麦胚凝集素选择性标记。 这 凝集素可逆地阻断输入细胞核。 单克隆 已经产生了针对这些核孔的抗体 糖蛋白和O-连接的GlcNAc被发现是 免疫决定子 这些发现提出了令人兴奋的可能性 细胞质糖基化可能参与组装， 核孔的功能。

The proper compartmentalization of proteins destined for the cell nucleus is likely to play a role in the regulation of cell growth and development. Synthetic peptides containing the amino acid sequence responsible for the nuclear localization of the SV40 Large T antigen and a modified sequence present in a cytoplasmic variant have been used to study protein import into the nucleus. These synthetic peptides have been used to generate polyclonal and monoclonal antibodies which bind specifically to the nuclear localization sequence. Such short peptides, when chemically coupled to the large fluorescent protein beta-phycoerythrin, specifically target the protein conjugate to the nucleus. Transport of such conjugates across the nuclear envelope was demonstrated after micro-infection into cultured cells or in an in vitro import assay using rat liver nuclei. Transport is time, temperature and energy dependent; only conjugates containing the localization sequence are properly transported. The nuclear pore complex transverses the nuclear envelope and may mediate uptake int0 the nucleus. We have shown that the outer nuclear membrane is an important site of membrane glycoprotein synthesis. We have also demonstrated that proteins bearing cytoplasmically oriented, O-linked GlcNAc are components of the nuclear pore complex. The nuclear pore glycoproteins can be selectively labelled using the lectin wheat germ agglutinin. This lectin reversibly blocks import into the nucleus. Monoclonal antibodies have been raised against these nuclear pore glycoproteins and O-linked GlcNAc was found to be part of the immunodeterminant. These findings raise the exciting possibility that cytoplasmic glycosylation may be involved in the assembly or functioning of the nuclear pore.