title: The human REC2/RAD51B gene acts as a DNA damage sensor by inducing G1 delay and hypersensitivity to ultraviolet irradiation.
abstract: HsRec2/Rad51B is a 350-amino acid protein with a molecular mass of 38,300 Da that appears to be involved in cell cycle regulation and UV-induced apoptosis. The mouse and human genes were isolated based on their homology to a recombinational repair gene from Ustilago maydis and contain functional domains to hRAD51 and hLIM 15 (M. C. Rice et al., Proc. Natl. Acad. Sci. USA, 94: 7417-7422, 1997). Here, we report the results of studies on the behavior of CHO cells containing a plasmid encoding a wild-type hsRec2/Rad51B, a full-length protein with a single mutation at residue 163, which lies in the putative src site, and a truncated version of hsRec2/Rad51B, containing only the first 100 amino acids at the NH2 terminus. Using fluorescence-activated cell sorting analysis to follow the progression of cells through the cell cycle, we find that stable transfectants constitutively overexpressing the wild-type human Rec2/Rad51B protein exhibit a G1 delay. In addition, when irradiated with UV at a dose of 15 J/m2, CHO cells transfected with the various hREC2/RAD51B vectors exhibited different responses. Cells expressing the wild-type human Rec2/Rad51B underwent apoptosis, with the greatest cell death occurring 24 h after irradiation. The control cells, which contained an empty vector, and the cells expressing truncated hsRec2/Rad51B or the full-length Rec2 with a mutation at residue 163 did not. In summary, these findings of cell cycle slowing and UV-induced apoptosis in CHO cells constitutively expressing the human Rec2/Rad51B protein suggest that hsRec2/Rad51B plays a role in a DNA damage surveillance pathway.
authors.affiliation: Department of Microbiology/Immunology, Kimmel Cancer Institute, Thomas Jefferson University, Philadelphia, Pennsylvania 19107, USA.
authors.forename: P A
authors.initials: PA
authors.lastname: Havre
authors.forename: M C
authors.initials: MC
authors.lastname: Rice
authors.forename: M
authors.initials: M
authors.lastname: Noe
authors.forename: E B
authors.initials: EB
authors.lastname: Kmiec
mesh_terms: D000818:Animals; D017209:Apoptosis; D016466:CHO Cells; D006224:Cricetinae; D004247:DNA / Q000528:radiation effects*; D004249:DNA Damage; D004268:DNA-Binding Proteins / Q000235:genetics*; D016193:G1 Phase; D006801:Humans; D051379:Mice; D011506:Proteins / Q000235:genetics*; D051135:Rad51 Recombinase; D013329:Structure-Activity Relationship; D014162:Transfection; D014466:Ultraviolet Rays
chemical_list: D004268:DNA-Binding Proteins; D011506:Proteins; C413002:RAD51B protein, human; D004247:DNA; C495153:RAD51 protein, human; D051135:Rad51 Recombinase; C495154:Rad51 protein, mouse