THE ROLE OF THE NUCLEAR ENVELOPE IN INTRACELLULAR PROTEIN SORTING

穿过核孔复合体的运输对于调节 细胞生长和正常发育。核孔的结构 以及它在核运输中的参与正在一个 分子水平。核孔复合体由一个家族组成 具有共价连接的O-连接N-的磷酸化糖蛋白 乙酰氨基葡萄糖。我们已经表达了主要的核孔 在细菌中表达糖蛋白p62，并在体外检测糖基化情况。 糖基化的p62也是通过在昆虫细胞中表达获得的 杆状病毒。P62的糖基化位点已经通过 缺失分析和蛋白酶谱分析。这种酶负责 核孔糖蛋白的糖基化已经部分地 从兔网织红细胞裂解液中提纯；正在尝试 从分子上克隆这种酶。 为了在体外检测核孔糖蛋白的功能， 运输，非洲爪哇提取物能够进行核组装和 已经使用了交通工具。利用该系统进行了演示。 核孔糖链中O-连接的N-乙酰氨基葡萄糖部分. 蛋白质可以在不改变核运输的情况下进行修饰。这些 提取物也被用来证明糖基化和 核孔糖蛋白在细胞内的磷酸化变化 周而复始。这一发现表明，可能存在一种协调的监管 糖基化和磷酸化，伴随着分解和 在细胞周期中核孔的重新组装。

Transport across the nuclear pore complex is essential for regulating cell growth and normal development. The structure of the nuclear pore and its involvement in nuclear transport are being studied at a molecular level. The nuclear pore complex is made up of a family of phosphorylated glycoproteins having covalently attached O-linked N- acetylglucosamine. We have expressed the major nuclear pore glycoprotein p62 in bacteria and examined the glycosylation in vitro. Glycosylated p62 is also obtained by expression in insect cells using baculovirus. The sites of glycosylation of p62 have been determined by deletion analysis and protease mapping. The enzyme responsible for glycosylation of the nuclear pore glycoproteins has been partially purified from rabbit reticulocyte lysate; an attempt is being made to molecularly cloning this enzyme. To examine the function of the nuclear pore glycoproteins in vitro, transport, Xenopus laevis extracts capable of nuclear assembly and transport have been employed. Using this system, it was demonstrated that the O-linked N-acetylglucosamine moiety of nuclear pore glyco- proteins can be modified without altering nuclear transport. These extracts have also been used to demonstrate that the glycosylation and phosphorylation of nuclear pore glycoproteins change during the cell cycle. The findings suggest that there may be a coordinate regulation of glycosylation and phosphorylation which accompany the breakdown and reassembly of the nuclear pore during the cell cycle.