C/G to A/T transversions represent the main type of mutation induced by gamma-irradiation in double-stranded M13mp10 DNA in a nitrogen-saturated solution.
To get more insight into the possible mutagenic consequences of DNA damage induced by radiation-generated H radicals (.H), a nitrogen-saturated solution of double-stranded (ds) M13mp10 DNA in phosphate buffer was irradiated with gamma-rays. Under these conditions 55% of the DNA-damaging species consists of H radicals and 45% of OH radicals (.OH). The mutations were investigated in a 144-bp mutational target sequence inserted into the lacZ alpha gene. A very specific mutation spectrum was obtained with respect to the type of mutations. Twenty out of the 28 radiation-induced mutations were C/G to A/T transversions; the remaining 8 mutations were 4 C/G to G/C transversions, 2 C/G to T/A transitions, one T/A to A/T transversion and only one -1 bp deletion. The mutations were rather randomly distributed along the 144-bp mutation target sequence with no clear mutational hot spots. When these results are compared with those we have obtained previously after irradiation of ds M13mp10 DNA under O2 (100% .OH) or N2O (90% .OH; 10% .H) (Hoebee et al., 1988, 1989), the data strongly suggest that H radicals may be responsible for the observed C/G to A/T transversions but not for -1 bp deletions.
Braun
J E
JE
Department of Medical Oncology, Vrije Universiteit, Amsterdam, The Netherlands.
Wanamarta
A H
AH
van den Akker
E
E
Lafleur
M V
MV
Retèl
J
J
D017104:Bacteriophage M13 / Q000235:genetics; D003037:Cobalt Radioisotopes / Q000633:toxicity; D004249:DNA Damage; D004252:DNA Mutational Analysis; D004279:DNA, Viral / Q000528:radiation effects*; D004926:Escherichia coli / Q000235:genetics; D005609:Free Radicals; D005720:Gamma Rays; D006859:Hydrogen / Q000633:toxicity; D007763:Lac Operon / Q000528:radiation effects; D016296:Mutagenesis; D016297:Mutagenesis, Site-Directed; D009153:Mutagens / Q000633:toxicity; D009584:Nitrogen / Q000633:toxicity*; D009609:Nitrous Oxide / Q000633:toxicity; D017354:Point Mutation; D011854:Radiochemistry; D017382:Reactive Oxygen Species / Q000633:toxicity; D014162:Transfection
D003037:Cobalt Radioisotopes; D004279:DNA, Viral; D005609:Free Radicals; D009153:Mutagens; D017382:Reactive Oxygen Species; D006859:Hydrogen; D009609:Nitrous Oxide; D009584:Nitrogen