DNA damage induced nucleotide excision repair in Saccharomyces cerevisiae.
Nucleotide excision repair (NER) is the most versatile and universal pathway of DNA repair that is capable of repairing virtually any damages other than a double strand break (DSB). This pathway has been shown to be inducible in several systems. However, question of a threshold and the nature of the damage that can signal induction of this pathway remain poorly understood. In this study it has been shown that prior exposure to very low doses of osmium tetroxide enhanced the survival of wild type Saccharomyces cerevisiae when the cells were challenged with UV light. Moreover, it was also found that osmium tetroxide treated rad3 mutants did not show enhanced survival indicating an involvement of nucleotide excision repair in the enhanced survival. To probe this further the actual removal of pyrimidine dimers by the treated and control cells was studied. Osmium tetroxide treated cells removed pyrimidine dimers more efficiently as compared to control cells. This was confirmed by measuring the in vitro repair synthesis in cell free extracts prepared from control and primed cells. It was found that the uptake of active (32)P was significantly higher in the plasmid substrates incubated with extracts of primed cells. This induction is dependent on de novo synthesis of proteins as cycloheximide treatment abrogated this response. The nature of induced repair was found to be essentially error free. Study conclusively shows that NER is an inducible pathway in Saccharomyces cerevisiae and its induction is dependent on exposure to a threshold of a genotoxic stress.
Singh
Rakesh Kumar
RK
Radiation Biology and Health Sciences Division, Bhabha Atomic Research Centre, Mumbai, India 400085. ksrakesh@yahoo.com
Krishna
Malini
M
D002470:Cell Survival; D004249:DNA Damage; D004260:DNA Repair; D004271:DNA, Fungal / Q000528:radiation effects; D004305:Dose-Response Relationship, Drug; D009993:Osmium Tetroxide; D011740:Pyrimidine Dimers; D012441:Saccharomyces cerevisiae / Q000235:genetics*; D013997:Time Factors; D014466:Ultraviolet Rays
D004271:DNA, Fungal; D011740:Pyrimidine Dimers; D009993:Osmium Tetroxide