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/
Jef. Braun et al., 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/, MUTATION RESEARCH, 289(2), 1993, pp. 255-263
To get more insight into the possible mutagenic consequences of DNA da
mage induced by radiation-generated H radicals (.H), a nitrogen-satura
ted solution of double-stranded (ds) M13mp10 DNA in phosphate buffer w
as irradiated with gamma-rays. Under these conditions 55% of the DNA-d
amaging species consists of H radicals and 45% of OH radicals (.OH). T
he mutations were investigated in a 144-bp mutational target sequence
inserted into the lacZalpha gene. A very specific mutation spectrum wa
s obtained with respect to the type of mutations. Twenty out of the 28
radiation-induced mutations were C/G to A/T transversions; the remain
ing 8 mutations were 4 C/G to G/C transversions, 2 C/G to T/A transiti
ons, one T/A to A/T transversion and only one -1 bp deletion. The muta
tions were rather randomly distributed along the 144-bp mutation targe
t sequence with no clear mutational hot spots. When these results are
compared with those we have obtained previously after irradiation of d
s 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 res
ponsible for the observed C/G to A/T transversions but not for -1 bp d
eletions.