Exposure to low dose of gamma radiation enhances the excision repair in XXXX .

@entity9871 @entity29815 @entity375 @entity7391 @entity7178
The effect of low doses of ionizing and nonionizing radiation on the radiation response of @entity375 @entity375 toward ionizing and nonionizing radiation was studied. The wild-type strain D273-10B on exposure to 54 Gy gamma radiation (resulting in about 10% cell killing) showed enhanced resistance to subsequent exposure to UV radiation. This induced UV resistance increased with the incubation time between the initial gamma radiation stress and the UV irradiation. Exposure to low doses of UV light on the other hand showed no change in gamma or UV radiation response of this strain. The strains carrying a mutation at @entity9871 behaved in a way similar to the wild type, but with slightly reduced induced response. In contrast to this, the @entity29815 mutants, defective in excision repair, showed no induced UV resistance. Removal of UV-induced @entity7391 dimers in wild-type @entity375 DNA after UV irradiation was examined by analyzing the sites recognized by UV endonuclease from @entity7178 . The samples that were exposed to low doses of gamma radiation before UV irradiation were able to repair the @entity7391 dimers more efficiently than the samples in which low gamma irradiation was omitted. The nature of enhanced repair was studied by scoring the frequency of induced gene conversion and reverse mutation at trp and ilv loci respectively in strain D7, which showed similar enhanced UV resistance induced by low-dose gamma irradiation. The induced repair was found to be essentially error-free. These results suggest that irradiation of strain D273-10B with low doses of gamma radiation enhances its capability for excision repair of UV-induced @entity7391 dimers.
