Histone nuclear proteins are irreversibly modified by reactive metabolites of diethylstilbestrol

Abstract

We demonstrate for the first time that diethylstilbestrol (DES), a synthetic estrogen, is converted by nuclei to histone-binding metabolite(s). Reaction of [3H]DES with nuclei in the presence of cumene hydroperoxide or NADPH revealed binding of [3H]DES to histone nuclear proteins. Gel electrophoresis experiments revealed that all five histones, 1, 2A, 2B, 3, and 4, were irreversibly bound to [3H]DES. Histones 1 and 3 were more susceptible to the attack by [3H]DES quinone, a metabolite of DES, than histones 2A, 2B, or 4. The kinetic constants, Km and Vmax, of this binding reaction in the presence of cumene hydroperoxide were 10 microM and 750 pmol/mg protein/30 min, respectively. This binding was significantly inhibited by cytochromes P-450 inhibitors. Low-molecular-weight thiols, such as glutathione and cysteine, or thiol modifiers, such as n-ethylmaleimide, dithionitrobenzoic acid, and hydroxymercuric benzoate, drastically inhibited binding of [3H]DES quinone to histone 3. The binding of [3H]DES metabolites to both transcriptionally active and inactive chromatin histone proteins was observed. We conclude that DES is metabolized to histone-binding metabolites, presumably by nuclear cytochrome P-450. DES quinone may be one of the histone-binding DES metabolites. These data suggest that an analogous in vivo modification in the transcriptionally active chromatin histones by DES metabolites may influence gene function.

Epigenomics, Pharmacoepigenomics, and Personalized Medicine in Cervical Cancer

“…DES exposure during pregnancy has been shown to alter the miRNA expression of oncogenic miRNAs in both fetus and mother [127] . Similarly, studies have also shown that DES affects histone modifications [128] . Warita et al [129] showed that the P450scc promoter region is deacetylated upon treatment with DES.…”