Development of highly efficient homologous recombination system using mouse recombination genes and establishment of mouse strains with gene engineered

小鼠RAD51基因是大肠杆菌recA和酵母RAD51基因的哺乳动物同源基因，这两个基因都参与了有丝分裂和减数分裂过程中的同源重组和DNA修复。在细胞周期同步化的小鼠M5S细胞中检测小鼠RAD51mRNA的表达。从G1期晚期到M期观察到RAD51转录本。在G1-S-G2期晚期，RAD51蛋白仅在细胞核中观察到。有丝分裂原激活小鼠脾T细胞和B细胞增殖，诱导RAD51mRNA的表达。免疫组织化学分析显示，小鼠RAD51蛋白存在于增殖细胞、睾丸的精原细胞、胸腺的未成熟T细胞、脾和肠道次级淋巴小结的生发中心细胞、卵巢的滤泡细胞和子宫和肠道的上皮细胞中。在减数分裂早期和中期的精母细胞和成熟前的静止卵母细胞中也有表达。因此，小鼠RAD51的表达与细胞的增殖状态密切相关，可能参与了精母细胞DNA修复、DNA复制以及减数分裂DNA重组。

The mouse Rad51 gene is a mammalian homologue of the Escherichia coli recA and yeast RAD51 genes, both of which are involved in homologous recombination and DNA repair in mitosis and meiosis. The expression of mouse Rad51 mRNA was examined in cell-cycle synchronized mouse m5S cells. The Rad51 transcript was observed from late G1 phase through to M phase. During the period of late G1-S-G2 phase, the RAD51 proteins were exclusively observed in nuclei. Activation of T cell and B cell proliferation in spleen by mitogens induced the expression of Rad51 mRNA.By immunohistochemical analyzes, the mouse RAD51 protein was detected in proliferating cells ; spermatogonia in testis, immature T cells in thymus, germinal center cells of the secondary lymphatic nodules of spleen and intestine, follicle cells in ovary and epithelial cells in uterus and intestine. It was also expressed in spermatocytes during the early and mid prophase of meiosis and in resting oocytes before maturation. Thus mouse Rad51 expression is closely related to the state of cell proliferation and is presumably involved in DNA repair coupled with DNA replication as well as meiotic DNA recombination in spermatocytes.