RESUMO
Cellular and genomic effects of post-treatment repair modulation by 2-deoxy-D-glucose (2-DG) and yeast extract were studied in 8-MOP + UVA treated cells of Saccharomyces cerevisiae. The type of lesions and their repair in phosphate buffer glucose (PBG) differed with UVA dose. At low UVA dose (1.4 kJ/m2), lesions were sublethal and mutagenic and did not repair by recombinogensis. The fraction of potentially lethal lesions and lesions repaired by recombinogenesis increased with UVA dose. Cellular repair in PBG was largely error-free and was inhibited by 2-DG. Yeast extract enhanced cellular repair and also recombinogensis; 2-DG in presence of yeast extract promoted error-prone repair. Pulsed-field gel electrophoresed chromosomal DNA bands did not show observable alterations immediately after 8-MOP + UVA treatment. On post-treatment incubation in PBG, the intensity ratio (rho n), of each band altered in a biphasic manner showing decrease first, followed by either increase or no change upto 24 hr depending upon UVA exposure dose. Presence of 2-DG in PBG inhibited decrease in rho n in a concentration dependent manner. Yeast extract reduced the time of first phase of DNA repair. 2-DG and yeast extract together reduced the time of first phase of repair and also inhibited the subsequent increase in rho n, which was observed in the case of yeast extract in PBG. It is proposed that (i) 2-DG in PBG inhibits excision of DNA damage and error-free repair; (ii) yeast extract stimulates the error-prone repair associated with cell cycle and recombinogenesis; (iii) 2-DG in presence of yeast extract allows excision of damage but inhibits build up through recombinogenesis inducing instead, cell cycle associated error-prone repair. A simple schematic model has been proposed to explain these events.