THE ROLE OF THE NUCLEAR ENVELOPE IN INTRACELLULAR PROTEIN SORTING

蛋白质的正确分类到细胞核已被证明 在调节细胞生长中发挥关键作用， 发展 当化学耦合到大荧光 蛋白质B-藻红蛋白，来自氨基酸的合成肽 SV 40大T抗原的酸性序列特异性靶向 与细胞核结合的蛋白质。 此类结合物的转运 在显微注射后，证实了穿过核膜 或在使用大鼠肝脏的体外输入测定中 原子核。 运输依赖于时间、温度和能量;只有 含有定位序列的缀合物被适当地 传送。 已经产生了结合 特别是这个序列。 这些抗体结合到完整的T 抗原和其他核蛋白，这表明该序列 通常暴露在分子的外表面， 输送到细胞核中。 核定位信号具有 在人类的一级结构中也发现了 糖皮质激素受体 10个残基的合成肽 从该受体的序列中衍生的序列足以指导 大分子进入细胞核的过程。 正在尝试 阻断糖皮质激素受体的核靶向作用。 核孔复合体穿过核膜， 介导细胞核的摄取。 实验室已经证明 携带细胞质定向的O-连接的G1 cNAc的蛋白质是 核孔复合体的组分。 核孔 糖蛋白可以选择性地标记使用肌动蛋白小麦 细菌凝集素 这种凝集素可逆地阻止两种输入 细胞核和RNA从细胞核输出到细胞核 细胞质 这些发现提出了一个令人兴奋的可能性， 细胞质糖基化可能参与组装， 核孔的功能。 单克隆抗体已经 针对这些核孔糖蛋白， 洁净. 来自主要核孔的序列信息 获得了蛋白质，并对该蛋白质进行了分子克隆。 核孔蛋白的结构和功能目前 用重组DNA技术来探测。

The proper sorting of proteins to the cell nucleus has been shown to play a key role in the regulation of cell growth and development. When chemically coupled to the large fluorescent protein B-phycoerythrin, synthetic peptides derived from the amino acid sequence of the SV40 Large T antigen specifically target the protein conjugate to the nucleus. Transport of such conjugates across the nuclear envelope was demonstrated after microinjection into cultured cells or in an in vitro import assay using rat liver nuclei. Transport was time, temperature and energy dependent; only conjugates containing the localization sequence were properly transported. Monoclonal antibodies have been generated which bind specifically to this sequence. These antibodies bind to intact T antigen, and other nuclear proteins, suggesting that the sequence is normally exposed on the outer surface of molecules to be transported into the nucleus. A nuclear localization signal has also been identified in the primary structure of the human glucocorticoid receptor. A synthetic peptide of 10 residues derived from the sequence of this receptor are sufficient to direct transport of large molecules into the nucleus. Attempts are being made to interrupt nuclear targeting of the glucocorticoid receptor. The nuclear pore complex traverses the nuclear envelope and mediates uptake to the nucleus. The laboratory has demonstrated that proteins bearing cytoplasmically oriented, O-linked G1cNAc are components of the nuclear pore complex. The nuclear pore glycoproteins can be selectively labelled using the actin wheat germ agglutinin. This lectin reversibly blocks both import into the nucleus and the export of RNA from the nucleus to the cytoplasm. These findings raise the exciting possibility that cytoplasmic glycosylation may be involved in the assembly or functioning of the nuclear pore. Monoclonal antibodies have been raised against these nuclear pore glycoproteins thus allowing their purification. Sequence information from the major nuclear pore protein was obtained and this protein has been molecularly cloned. The structure and function of the nuclear pore protein is currently being probed using recombinant DNA technology.