CELL-CYCLE DEPENDENT EXPRESSION OF THE MOUSE RAD51 GENE IN PROLIFERATING CELLS

The mouse Rad51 gene is a mammalian homologue of the Escherichia coli recA and yeast RAD51 genes, both of which are involved in homologous r ecombination and DNA repair in mitosis and meiosis. The expression of mouse Rad51 mRNA was examined in synchronized mouse m5S cells, The Rad 51 transcript was observed from late G1 phase through to M phase, Duri ng the period of late G1-S-G2, the RAD51 proteins were observed exclus ively in nuclei. Activation by mitogens of T cell and B cell prolifera tion in spleen induced the expression of Rad51 mRNA, By immunohistoche mical analyses, the mouse RAD51 protein was detected in proliferating cells: spermatogonia in testis, immature T cells in thymus, germinal c enter 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 early and mid-prophase of meiosis and in resting oocytes before maturation. Thus, mouse Ran5 1 expression is closely related to the state of cell proliferation and is presumably involved in DNA repair coupled with DNA replication, as well as in meiotic DNA recombination in spermatocytes.