A mouse homolog of the Escherichia coli recA and Saccharomyces cerevisiae RAD51 genes.

Analysis of mitotic and meiotic recombination in mammalian cells has been hampered by the complexity of the reactions involved as well as lack of mutants. Furthermore, none of the genes involved in the process has yet been identified. In budding yeast, Saccharomyces cerevisiae, the RAD51 gene is essential along with other genes of the RAD52 epistasis group for mitotic and meiotic recombination and DNA repair. The Rad51 protein is structurally similar to Escherichia coli RecA protein, which is required in homologous recombination and SOS responses in bacteria. Here we report the isolation of a mouse homolog of the yeast RAD51 gene. The amino acid sequence predicted from the gene shows 83% and 55% homology with those of the yeast RAD51 and the E. coli recA product, respectively. The mouse gene complemented a rad51 mutation of S. cerevisiae with sensitivity to methyl-methanesulfonate, which produces double-strand breaks of DNA. This gene is expressed in the thymus, testis, ovary, spleen, and intestine, suggesting that its product is involved in mitotic and meiotic recombination in addition to DNA repair. IMAGES:

对哺乳动物细胞中有丝分裂重组与减数分裂重组的研究，曾因相关反应的复杂性以及突变体的匮乏而受阻。此外，该过程所涉及的基因至今尚未被鉴定。在酿酒酵母（Saccharomyces cerevisiae）中，RAD51基因与RAD52上位性组的其他基因一同，是有丝分裂重组、减数分裂重组以及DNA修复所必需的。Rad51蛋白的结构与大肠杆菌（Escherichia coli）RecA蛋白相似，后者在细菌的同源重组与SOS应答过程中发挥必需作用。本研究成功分离得到了酿酒酵母RAD51基因的小鼠同源基因。该基因预测得到的氨基酸序列，分别与酿酒酵母RAD51蛋白、大肠杆菌RecA蛋白的序列具有83%和55%的同源性。该小鼠基因能够互补酿酒酵母的rad51突变体对甲基磺酸甲酯（methyl-methanesulfonate，可诱导DNA双链断裂）的敏感性。该基因在胸腺、睾丸、卵巢、脾脏与肠道中均有表达，提示其编码产物除参与DNA修复外，还参与了有丝分裂重组与减数分裂重组过程。IMAGES: