Practical Improvement of Signal Sequence Trap Method

信号序列陷阱（Signal Sequence Trap， SST）方法是一种高效克隆秘书蛋白和I型跨膜蛋白的方法。美国风险投资公司Genentech的一个独立研究小组在我们的报告的基础上报道了一种利用酵母转化酶分泌到细胞中的新方法（Klein， RD,et . proc Natl acad . sci . u.s.a 1996,93）（14）： 7108)。对比我们原来的SST方法和Genentech的新方法，新方法比我们原来的方法有效10000倍。然后，我们认为采用新方法是合理的，而不是改进我们的原方法。我们用新的酵母法开始了大规模的筛选。以SST法获得的cDNA片段为基础，克隆出全长cDNA。接下来，通过在Cos细胞中表达cDNA's获得cDNA's的基因产物。我们分析了这些蛋白是否对血细胞的发育和分化有一定的影响。为此，我们利用小鼠胚胎干细胞在OP9基质细胞（OP9系统）上的体外分化诱导。这项分析正在进行中，然而，还没有发现含有对血细胞发育和分化有显著影响的cDNA。

Signal Sequence Trap (SST) method is an efficient cloning strategy for secretary proteins and type I transmembrane proteins and the method was innovated by our group. An independent research group of Genentech, a venture company in USA,reported a novel method by using secretion of yeast invertase out to the cells based on our report (Klein, RD,et al.Proc Natl Acad.Sci.U.S.A.1996,93 (14) : 7108). Comparing our original SST method and Genentech's novel method, the novel method turns out to be far more effective than our original method by a magnitude of 10,000. Then, we consider it reasonable to adapt the new method, instead of improving our original method. We start a large scale screening by using the novel yeast method.Based on the cDNA fragment obtained by SST method, full length cDNA's were cloned. Next, gene products of the cDNA's were obtained by expressing the cDNA's in Cos cells. We analyzed whether those proteins obtain some effects on the development and differentiation of blood cells. For this purpose, we utilized in vitro differentiation induction from mouse embryonic stem cells on OP9 stromal cells (OP9 system). This analysis is under way, however, no cDNA's containing significant effects on the development and differentiation of blood cells have been obtained.