THIOPYRONINE-SENSITIZED AND 8-METHOXYPSORALEN-SENSITIZED PHOTODYNAMICEFFECT ON CELL-GROWTH, COLONY-FORMING ABILITY AND RNA-SYNTHESIS IN SACCHAROMYCES MUTANTS DEFICIENT IN DNA-REPAIR

We compared the photodynamic effects of thiopyronine (TP) and visible light, and 8-methoxypsoralen (8-MOP) and ultraviolet A (UV-A) light, o n growth, colony forming ability and RNA synthesis in a repair-profici ent Saccharomyces strain and three mutants deficient in DNA repair mec hanisms (DNA repair assays). With 8-MOP and UV-A repair-deficient muta nts were significantly more sensitive than the repair-proficient strai n indicating that the system is sensitive for the detection of DNA dam age. With TP and visible light, the photodynamic effects were comparab le in the mutants and the control, indicating no DNA damage. These res ults support previous work showing that the main target of TP photosen sitization in eukaryotes is not nuclear DNA.