Unique response of double-stranded oligonucleotides containing a single 8-oxo-7,8-dihydroguanine to gamma rays in the frozen aqueous state at 77 K

Two kinds of double-stranded oligonucleotides containing a single 8-oxo-7,8 -dihydroguanine were labeled with P-32 at their 5' ends and exposed to gamm a rays in the frozen aqueous state at 77 K, where both direct and quasi-dir ect effects of ionizing radiation predominate. Analysis of the oligonucleot ides with 20% denaturing polyacrylamide gel electrophoresis revealed no dif ference in the immediate induction of strand breaks between oligonucleotide s containing 8-oxo-7,8-dihydroguanine and their corresponding oligonucleoti des with normal guanine, but piperidine-sensitive damage was induced more f requently in the former than in the latter. Sequence analysis of irradiated oligonucleotides showed that not only 8-oxo-7,8-dihydroguanine but also it s neighboring bases and the cytosine residue that is paired to it became pi peridine-sensitive in both oligonucleotides, These results suggest that 8-o xo-7,8-dihydroguanine, its neighboring bases and the opposite cytosine are candidates for radiation damage hot spots. (C) 2000 by Radiation Research S ociety.