engleski

Modulation of apurinic (AP) endonuclease activity in mammalian cells: transfection of yeast, but not human AP endonuclease renders cells more resistant to genotoxic agents

Abasic sites are ubiquitous DNA lesions that arise spontaneously or are induced by DNA damaging agents. They block DNA replication and are cytotoxic and mutagenic. Key enzymes involved in repair of abasic sites are apurinic/apyrimidinic endonucleases (APendo). To analyze the role of APendo in protection of mammalian cells against DNA damaging agents, we have transfected both the human (APE) and the yeast (APN1) AP endonuclease in Chinese hamster cells and compared the effects of expression of these genes in stable transfectants regarding survival of cells and chromosomal aberration formation. Although APE was markedly expressed on RNA and protein level, nuclear extracts of human APE transfectants did not show a higher APendo activity than the parental line and became not more resistant to the cell kiling and clastogenic effect of methyl methanesulfonate and hydrogen peroxide. In constrast, cells transfected with the yeast APN1 gene expressed higher APendo activity and became clearly more resistant to the cytotoxic and chromosome breakage inducing activity of the agents. The results indicate that the excision repair capacity and mutagen resistance can be enhanced by introducing, in mammalian cells, a yeast DNA repair gene. They also verify that AP sites are both cytotoxic and clastogenic lesions.

mammalian cells; apurinic endonuclease activity; genotoxic agents

nije evidentirano