Belin D, Wohlwend A, Schleuning W D, Kruithof E K, Vassalli J D
Département de Pathologie, University of Geneva Medical Center, Switzerland.
EMBO J. 1989 Nov;8(11):3287-94. doi: 10.1002/j.1460-2075.1989.tb08489.x.
Two forms of plasminogen activators inhibitor 2 (PAI-2) are synthesized by human and murine monocytes/macrophages: one accumulates in the cytosol, while the other is translocated into the endoplasmic reticulum, glycosylated and secreted. We show here that a single mRNA encodes both forms of PAI-2. Firstly, a single PIA-2 mRNA was detected by Northern blot hybridization and by RNase protection. Secondly, transfection of a PAI-2 cDNA led to the synthesis of both forms of PAI-2. Finally, in vitro translation of an mRNA transcript of the PAI-2 cDNA in the presence of microsomal membranes generated two topologically distinct forms of PAI-2. The cytosolic and secreted forms of PAI-2 do not result from the use of two translation start sites, since their synthesis initiates at the same AUG, in a sequence context that is conserved between the human and murine genes. Thus, the accumulation of one polypeptide into two topologically distinct cellular compartments can be achieved by facultative translocation.
人及小鼠单核细胞/巨噬细胞可合成两种形式的纤溶酶原激活物抑制剂2（PAI-2）：一种积聚在胞质溶胶中，而另一种则转运至内质网，进行糖基化并分泌。我们在此表明，单一的信使核糖核酸（mRNA）编码两种形式的PAI-2。首先，通过Northern印迹杂交和核糖核酸酶保护检测到单一的PAI-2 mRNA。其次，转染PAI-2互补脱氧核糖核酸（cDNA）导致两种形式的PAI-2均得以合成。最后，在微粒体膜存在的情况下对PAI-2 cDNA的信使核糖核酸转录本进行体外翻译，产生了两种拓扑结构不同的PAI-2形式。PAI-2的胞质溶胶形式和分泌形式并非源于使用两个翻译起始位点，因为它们的合成起始于同一个甲硫氨酸密码子（AUG），且在人和小鼠基因之间的序列背景中是保守的。因此，通过兼性转运可使一种多肽积聚到两个拓扑结构不同的细胞区室中。
