Wilson J H, Leung W Y, Bosco G, Dieu D, Haber J E
Department of Biochemistry, Baylor College of Medicine, Houston, TX 77030.
Proc Natl Acad Sci U S A. 1994 Jan 4;91(1):177-81. doi: 10.1073/pnas.91.1.177.
We have compared the efficiency of transformation by linear DNA fragments in yeast strains carrying different numbers of homologous targets for recombination. In strains carrying dispersed copies of a target and in strains carrying tandem arrays, the frequency of transformation is proportional to the number of targets. This result is in contrast to previous studies of transformation in mammalian cells, where targeted integration was insensitive to the number of targets. We conclude that, in yeast, the search for a homologous partner is a rate-limiting step in the successful recombination of linearized DNA fragments. Furthermore, the fact that we obtain the same results with both dispersed and clustered targets argues against models of homology searching in which DNA becomes nonspecifically associated with a chromosome and then slides along the DNA until homology is encountered.
我们比较了携带不同数量同源重组靶点的酵母菌株中线性DNA片段的转化效率。在携带靶点分散拷贝的菌株和携带串联阵列的菌株中，转化频率与靶点数量成正比。这一结果与之前对哺乳动物细胞转化的研究形成对比，在哺乳动物细胞中，靶向整合对靶点数量不敏感。我们得出结论，在酵母中，寻找同源配对物是线性化DNA片段成功重组的限速步骤。此外，我们在分散靶点和聚集靶点上都获得了相同结果，这一事实与同源性搜索模型相悖，在这些模型中，DNA与染色体非特异性结合，然后沿着DNA滑动，直到遇到同源性。
