Model system to study classical nuclear export signals

Signal-mediated protein transport through the nuclear pore complex is of considerable interest in the field of molecular pharmaceutics. Nuclear localization signals can be used to target genes/antisense delivery systems to the nucleus Studying nuclear export is useful in enhancing the expression and the efficiency of action, of these therapeutic agents. The mechanism of nuclear import has been well studied and most of the proteins participating in this mechanism have been identified. The subject of nuclear export is still in the initial stages and there is a considerable amount of uncertainty in this area. Two main export receptors identified so far are Exportin 1 (Crm1) and Calreticulin. Crm1 recognizes certain leucine-rich amino acid sequences in the proteins it exports called classical nuclear export signals. This paper describes a model system to study, identify, and establish these classical nuclear export signals using green fluorescent protein (GFP). Two putative export signals in the human progesterone receptor (PR) and the strongest nuclear export signal known (from mitogen activated protein kinase kinase [MAPKK]) were studied using this model system.

在分子药剂学领域，信号介导的蛋白质通过核孔复合体的转运备受关注。核定位信号可用于将基因/反义递送系统靶向细胞核。研究核输出对于提高这些治疗剂的表达和作用效率是有用的。核输入机制已得到充分研究，参与该机制的大多数蛋白质已被确定。核输出这一课题仍处于初始阶段，在这一领域存在大量不确定性。到目前为止确定的两种主要输出受体是输出蛋白1（Crm1）和钙网蛋白。Crm1识别其输出的蛋白质中某些富含亮氨酸的氨基酸序列，这些序列被称为经典核输出信号。本文描述了一个利用绿色荧光蛋白（GFP）研究、识别和确定这些经典核输出信号的模型系统。利用该模型系统研究了人孕酮受体（PR）中的两个假定输出信号以及已知最强的核输出信号（来自丝裂原活化蛋白激酶激酶[MAPKK]）。