Cell cycle-dependent expression of the mouseRad51 gene in proliferating cells

Abstract
The mouseRad51 gene is a mammalian homologue of theEscherichia coli recA and yeastRAD51 genes, both of which are involved in homologous recombination and DNA repair in mitosis and meiosis. The expression of mouseRad51 mRNA was examined in synchronized mouse m5S cells. TheRad51 transcript was observed from late G1 phase through to M phase. During the period of late G1-S-G2, the RAD51 proteins were observed exclusively in nuclei. Activation by mitogens of T cell and B cell proliferation in spleen induced the expression ofRad51 mRNA. By immunohistochemical analyses, 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 early and mid-prophase of meiosis and in resting oocytes before maturation. Thus, mouseRad51 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.