Oxidative damage to methyl-CpG sequences inhibits the binding of the methyl-CpG binding domain (MBD) of methyl-CpG binding protein 2 (MeCP2)

Abstract

Cytosine methylation in CpG dinucleotides is believed to be important in gene regulation, and is generally associated with reduced levels of transcription. Methylation-mediated gene silencing involves a series of DNA-protein and protein-protein interactions that begins with the binding of methyl-CpG binding proteins (MBPs) followed by the recruitment of histone-modifying enzymes that together promote chromatin condensation and inactivation. It is widely known that alterations in methylation patterns, and associated gene activities, are often found in human tumors. However, the mechanisms by which methylation patterns are altered are not currently understood. In this paper, we investigate the impact of oxidative damage to a methyl-CpG site on MBP binding by the selective placement of 8-oxoguanine (8-oxoG) and 5-hydroxymethylcytosine (HmC) in a MBP recognition sequence. Duplexes containing these specific modifications were assayed for binding to the methyl-CpG binding domain (MBD) of one member of the MBP family, methyl-CpG binding protein 2 (MeCP2). Our results reveal that oxidation of either a single guanine to 8-oxoG or of a single 5mC to HmC, significantly inhibits binding of the MBD to the oligonucleotide duplex, reducing the binding affinity by at least an order of magnitude. Oxidative damage to DNA could therefore result in heritable, epigenetic changes in chromatin organization.

Dietary factors, epigenetic modifications and obesity outcomes: Progresses and perspectives

“…Replacement of guanine to 8-hydroxy 2'-deoxy-guanosine (8-OHdG), one of the major DNA oxidative damage by-products, substantially diminishes the binding of methylCpG binding proteins (important to manage site-specific chromatin organization and transcriptional repression) and results in heritable epigenetic changes (Valinluck et al, 2004). In addition, some DNA lesions have been shown to interfere with the ability of DNA to function as a substrate for the DNA methyl transferases (DNMTs), resulting in global hypomethylation (Zhang et al, 2007).…”

LINE-1 gene hypomethylation and p16 gene hypermethylation in HepG2 cells induced by low-dose and long-term triclosan exposure: The role of hydroxyl group

“…It is known that 8-OHdG may lead to hypomethylation by inhibiting the binding of DNMTs to DNA by a steric block and also inhibiting the binding of methylated-DNA to MBDs, both of which are important to maintain DNA methylation (Valinluck et al, 2004). Our previous data had shown that 8-OHdG inhibitor NAC mitigated TCSmediated decrease of GDM in HepG2 cells (Ma et al, 2013).…”

Synthesis and Thermodynamic Studies of Oligodeoxyribonucleotides Containing Tandem Lesions of Thymidine Glycol and 8-Oxo-2‘-deoxyguanosine

“…Damage occurring at CpG dinucleotide and the resulting mutation at these sites may perturb the binding of DNA to methyl-CpG binding proteins (55). We reason that the type of tandem lesion that we synthesized here may have implications in CpG mutagenesis.…”