Reconstitution analysis of mating type switching recombination of fission yeast Schizosaccharomyces pombe

在分裂酵母裂糖酵母（Schizosaccharomyces pombe）中，交配类型的转换是通过同源重组机制发生的。Swi2-Swi5蛋白复合物被认为在交配类型转换过程中基因转换的启动中起重要作用。为了揭示该复合物的生化功能，我纯化了Swi2-Swi5蛋白复合物，分析了其生化活性，并从研究中带来了两个重要发现。第一种，Swi2至少有两个DNA结合域；一个位于含有at钩基序的n端，另一个位于c端。其次，Swi2-Swi5复合物促进D-loop的形成，这是链交换反应起始的重要活性。一个n端截断的Swi2蛋白与缺少n端DNA结合结构域的Swi5络合，促进了d环的形成，这表明Swi2的c端区域具有d环活性的必要结构域。这些结果有力地表明，Swi2-Swi5直接参与了交配型转换过程中的链交换反应。

In fission yeast Schizosaccharomyces pombe, mating type switching occurs at mat locus by using a mechanism of homologous recombination. The Swi2-Swi5 protein complex is considered to play an important role in the initiation of gene conversion during mating type switching. To reveal the biochemical function of the complex, I purified the Swi2-Swi5 protein complex, analyzed its biochemical activities and brought two important findings from the study. The first, Swi2 has at least two DNA binding domains; one is located at the N-terminal region which contains AT hook motif, and the other is located at the C-terminal region. The second, the Swi2-Swi5 complex promotes D-loop formation, which is an essential activity for initiation of strand exchange reaction. An N-terminal truncated Swi2 protein complexed with Swi5, which lacks the N-terminal DNA binding domain, promotes still D-loop formation, indicating that The C-terminal region of Swi2 has the essential domain for the D-loop activity. These results strongly suggest that Swi2-Swi5 directly involved in strand exchange reaction during mating type switching.