D. Roy et Dn. Pathak, HISTONE NUCLEAR PROTEINS ARE IRREVERSIBLY MODIFIED BY REACTIVE METABOLITES OF DIETHYLSTILBESTROL, Journal of toxicology and environmental health, 44(4), 1995, pp. 449-459
We demonstrate for the first time that diethylstilbestrol (DES), a syn
thetic estrogen, is converted by nuclei to histone-binding metabolite(
s). Reaction of [H-3]DES with nuclei in the presence of cumene hydrope
roxide or NADPH revealed binding of [H-3]DES to histone nuclear protei
ns. Cel electrophoresis experiments revealed that all five histones, 1
, 2A, 2B, 3, and 4, were irreversibly bound to [H-3]DES. Histones 1 an
d 3 were more susceptible to the attack by [H-3]DES quinone, a metabol
ite of DES, than histones 2A, 2B, or 4. The kinetic constants, K-m and
V-max of this binding reaction in the presence of cumene hydroperoxid
e were 10 mu M and 750 pmol/mg protein/30 min, respectively. This bind
ing was significantly inhibited by cytochromes P-450 inhibitors. Low-m
olecular-weight thiols, such as glutathione and cysteine, or thiol mod
ifiers, such as n-ethylmaleimide, dithionitrobenzoic acid, and hydroxy
mercuric benzoate, drastically inhibited binding of [H-3]DES quinone t
o histone 3. The binding of [H-3]DES metabolites to both transcription
ally active and inactive chromatin histone proteins was observed. We c
onclude that DES is metabolized to histone-binding metabolites, presum
ably by nuclear cytochromes P-450. DES quinone may be one of the histo
ne-binding DES metabolites. These data suggest that an analogous in vi
vo modification in the transcriptionally active chromatin histones by
DES metabolites may influence gene function.