K. Hiramoto et al., DNA-BASE AND DEOXYRIBOSE MODIFICATION BY THE CARBON-CENTERED RADICAL GENERATED FROM 4-(HYDROXYMETHYL)BENZENEDIAZONIUM SALT, A CARCINOGEN INMUSHROOM, Chemical research in toxicology, 8(3), 1995, pp. 356-362
Modification of the base and the sugar moieties of DNA with 4-(hydroxy
methyl)benzenediazonium salt (HMBD), a carcinogen in the mushroom Agar
icus bisporus, was investigated. When deoxyribonucleosides dGuo, dAdo,
dThd, and dCyd were incubated with HMBD at pH 7.4 and 37 degrees C, t
he levels of all the nucleosides were decreased. The decrease was inhi
bited by ethanol or Cys. When deoxyribose was incubated with HMBD, mal
onaldehyde was released as assessed by the thiobarbituric acid reactiv
ity. The release was inhibited by ethanol. Major products of the react
ion of dGuo and dAdo with HMBD were isolated, and their structures wer
e established to be 8-[4-(hydroxymethyl)phenyl]dGuo (8-HMP-dGuo) and 8
-[4-(hydroxymethyl)phenyl]dAdo (8-HMP-dAdo), respectively. Calf thymus
DNA treated with HMBD was enzymatically digested into nucleosides, in
which 8-HMP-dGuo and 8-HMP-dAdo were detected. Formation of the modif
ied nucleosides in DNA was inhibited by ethanol or 2-mercaptoethanol.
Malonaldehyde was released from DNA treated with HMBD, which indicated
that the deoxyribose moiety of DNA had been damaged. The results indi
cate that the 4-(hydroxymethyl)phenyl radical generated from HMBD can
directly modify the base and the sugar moieties of DNA under the mild
conditions. Inhibitory effect of ethanol was ascribable to its scaveng
ing activity for the carbon-centered radical. The inhibitory effect of
Cys and 2-mercaptoethanol was found to be due to the formation of the
reversible adducts between HMBD and the SH compounds.