Defective Brca2 influences topoisomerase I activity in mammalian cells.
The Chinese hamster cell mutant V-C8 is defective in the Brca2 gene (Kraakman-van der Zwet et al., 2002, Cell Biol.; 22: 669). Here we report that V-C8 cells were 10-fold more sensitive to camptothecin, an inhibitor of topoisomerase I, than the parental V79 cells. The level of the relaxation activity of topoisomerase I in nuclear extracts was also lower (4-fold) in V-C8 than V79 cells, in spite of the fact that the level of the topoisomerase I protein was the same in these cells. The survival of V-C8 cells in the presence of camptothecin, the sensitivity of V-C8 topoisomerase I to camptothecin, and the level of the relaxation activity in V-C8 nuclear extract were almost completely restored by transfection of V-C8 cells with the murine Brca2 gene or by the transfer of human chromosome 13 providing the BRCA2 gene. These results indicate that the observed changes in the topoisomerase I activity in V-C8 are due to the defective function of the Brca2 gene.
Rahden-Staroń
Iwonna
I
Department of Biochemistry, Medical University of Warsaw, Warszawa, Poland. ivrahden@amwaw.edu.pl
Szumiło
Maria
M
Grosicka
Emilia
E
Kraakman van der Zwet
Maria
M
Zdzienicka
Małgorzata Z
MZ
D000818:Animals; D024682:BRCA2 Protein / Q000235:genetics* / Q000378:metabolism*; D002166:Camptothecin / Q000494:pharmacology*; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects*; D002882:Chromosomes, Human, Pair 13; D006224:Cricetinae; D004264:DNA Topoisomerases, Type I / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D051379:Mice; D011994:Recombinant Proteins / Q000378:metabolism; D059004:Topoisomerase I Inhibitors; D014162:Transfection
D024682:BRCA2 Protein; D011994:Recombinant Proteins; D059004:Topoisomerase I Inhibitors; D004264:DNA Topoisomerases, Type I; D002166:Camptothecin