THE ROLE OF THE NUCLEAR ENVELOPE IN INTRACELLULAR PROTEIN SORTING

对运往细胞的蛋白质进行适当的分隔 细胞核可能在调节细胞生长和生长方面发挥作用 发展。含有该氨基酸的合成肽 负责SV40核定位的序列 大T抗原和存在于细胞质中的修饰序列 变异体已被用于研究蛋白质进入细胞核的情况。 这些合成肽已经被用来产生多克隆 以及与细胞核特异结合的单抗 本地化序列。这样的短肽，当化学上 与大型荧光蛋白β-藻红蛋白偶联， 将蛋白质结合物特定地定位于细胞核。 这种偶联物在核膜上的运输是 在微感染培养细胞后或在 采用大鼠肝细胞核进行体外进口试验。交通就是时间， 依赖于温度和能量；只有包含 定位序列被正确传输。核孔 复合体横穿核膜，可能在 摄取进入细胞核。我们已经证明了外核子 膜是膜糖蛋白的重要结合部位 综合。我们还证明了含有 面向细胞质、O-连接的GlcNAc是 核孔复合体。核孔糖蛋白可以是 用凝集素麦芽凝集素选择性标记。这 单克隆 已经针对这些核孔产生了抗体 糖蛋白和O-连接的GlcNAc被发现是 免疫决定簇。这些发现提出了令人兴奋的可能性 这种细胞质糖基化可能参与组装或 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.