Hydroxyphenylation of Histone Lysines: Post-translational Modification by Quinone Imines

Abstract

Monocyclic aromatic amines are widespread environmental contaminants with multiple sources such as combustion products, pharmaceuticals, and pesticides. Their phenolic metabolites are converted intracellularly to electrophilic quinone imines upon autoxidation and can embed in the cellular matrix through a transimination reaction that leaves a redox-active residue as a substituent of lysine side-chain amino groups. To demonstrate the occurrence of this process within the cellular nucleus, Chinese hamster ovary AA8 cells were treated with the para-phenol of 3,5-dimethylamine, after which the histone proteins were isolated, derivatized, and subjected to tryptic digestion. The resulting peptides were analyzed by tandem mass spectrometry to determine which lysines were modified. Nine residues in histones H2A, H2B, and H4 were identified; these were located in histone tails, close to where DNA makes contact with the nuclear core particle, elsewhere on the protein surface, and deep within the core. Kinetics of disappearance of the modified lysines in cultured cells was determined using isotope-dilution mass spectrometry. AA8 cells were also transfected with the genetically encoded hydrogen peroxide biosensor HyPer in constructs that lead to expression of HyPer in different cellular compartments. Challenging the resulting cells with the dimethylaminophenol resulted in sustained fluorescence emission in each of the compartments, demonstrating ongoing production of H2O2. The kinetics of modified lysine loss determined by mass spectrometry was consistent with persistence of HyPer fluorescence emission. We conclude that the para-phenol of 3,5-dimethylamine can become stably integrated into the histone proteins, which are minimally repaired if at all, and function as a persistent source of intracellular H2O2.

Haloquinone Chloroimides as Toxic Disinfection Byproducts Identified in Drinking Water

“…Halobenzoquinones were also confirmed to be of high cytotoxicity and induced reproductive and developmental toxicity . Semiquinone-free radicals of HQCs may cause the production of ROS, further cause DNA damage or combine with the mercapto groups of histones and subsequently integrate into proteins to form adducts in living cells. − Levels of intracellular ROS at the concentration of IC 50 in HepG2 cells after a 24 h exposure to five HQCs are shown in Figure S4. It is shown that all five tested HQCs exhibited the ability to generate ROS, which partially supported that excessive production of ROS in HepG2 cells may be one of the mechanisms causing cytotoxicity of HQCs.…”

“…25,26 HQCs could also react with the sulfhydryl groups of histones as electrophiles and integrate into proteins to form adducts. 27 The octanol−water partition coefficients of HQCs increased as a function of the halogen substitution degree, which indicated that HQCs were more difficult to be metabolized and excreted in organisms than quinone imines. 28 We calculated the toxicity of HQCs using computational toxicology software EPI Suite, which was developed by the US National Environmental Protection Agency and the US Syracuse Research Corporation, and widely used for predication of toxicity.…”

“…Especially, quinone imine homologues, which are analogues of HQCs, exhibited a high redox activity and could produce reactive oxygen species (ROS) . The ROS could further promote inflammation, activate immune cells embedded in nucleosomes, and induce DNA damage in biological systems. , HQCs could also react with the sulfhydryl groups of histones as electrophiles and integrate into proteins to form adducts . The octanol–water partition coefficients of HQCs increased as a function of the halogen substitution degree, which indicated that HQCs were more difficult to be metabolized and excreted in organisms than quinone imines .…”

Dihydroceramide Desaturase Functions as an Inducer and Rectifier of Apoptosis: Effect of Retinol Derivatives, Antioxidants and Phenolic Compounds

“…9 Structures of study compounds used and of putative quinonoid oxidation intermediates hypothesised to be involved in the induction of Degs1 polyubiquitination en route to hydroxycelecoxib (Fig. 9, Box 2), which is a known metabolite [24][25][26][27][28][29]. In principle, protonation and dehydration of the latter might also generate an intermediate pyrazolium species with quinone methide character (Fig.…”

“…9, Box 2). Quinone imines and related quinonoid species are redox-active entities and also have the potential to covalently modify biomolecular targets [24][25][26][27][28][29]. In this regard it is interesting that acetaminophen, which is known to generate N-acetyl-p-benzoquinone imine as a potentially toxic metabolite in vivo [30,31], does not induce polyubiquitination of Degs1 whereas the longer chain counterpart, 4-HPA, does induce polyubiquitination.…”