M. PESHEVA2, O. KRASTANOVA2, M. HADZHITODOROV1, T. STOYCHEVA1, V. DENTCHEVA2, Y. ZHECHEVA1, P. VENKOV1 and Ts. TSVETKOV1
1 Institute of Cryobiology and Food Technology, Dept. of Molecular Ecology, BG-1407 Sofia, Bulgaria
2 Sofia University, Faculty of Biology, Dept. of Genetics, BG-1421 Sofia, Bulgaria
PESHEVA, M., O. KRASTANOVA, M. HADZHITODOROV, T. STOYCHEVA, V. DENTCHEVA, Y. ZHECHEVA, P. VENKOV and Ts. TSVETKOV, 2004. Improved monitoring of environmental carcinogens. Bulg. J. Agric. Sci., 10: 221–228
An assay based on induction of transposition of Ty1 elements in Saccharomyces cerevisiae is proposed. A tester strain was developed that contains a Ty1 element, marked with the indicator gene HIS3AI (Curcio and Garfinkel, 1991), which allows following the transposition in the genome as a whole and the ts1 mutation, which increases cellular permeability (Staleva et al., 1996). Hypersensitivity to chemical agents, higher cell wall porosity and transformability with plasmid DNA without treatment of cells with lithium kations evidenced an enhanced cellular permeability of the tester cells. The increased permeability resulted in higher sensitivity to carcinogens. The treatment with laboratory carcinogens (EMS, MMS, 4NQO, benzo(a)pyrene) induced Ty1 transposition rates by a factor of 10 to 20, compared to the controls. The induction is not stress-generated by the cytotoxicity of carcinogens, since treatment with NaN3 at concentrations killing 50 % of the cells did not increase the transposition rate. The increase of Ty1 transposition in tester cells is specific for carcinogens active in yeast and treatment with benzo(a)pyrene induced the transposition only in presence of S9 mix. The Ty1 transposition test responded positively to a number of Ames-test negative carcinogens. Dichloromethane, acetamide and thioacetamide, showing positive response only in DEL test, were also positive in the Ty1 test. Three out of five studied DEL negative carcinogens induced Ty1 transposition. Although moderate, the positive response of Ty1 test to furfuryl alcohol, tert-butyl-hydroquinoline and tetrahydrofuran was statistically significant and verified in kinetics and concentration-dependent experiments. It is concluded, that the Ty1 transposition assay can be used as a short-term test for detection of carcinogens.