Abstract
Recently, “Exposome” was proposed as a total lifetime exposure by C. Wild. Most studies have focused on lifetime exposure; however, the molecular mechanisms remain unclear. Therefore, in this study, we focused on DNA methylation, which epigenetically regulates gene expression, and analyzed the effects of environmental electrophiles that easily bind to proteins as a model for the exposome study.
First, we examined the effects of 45 electrophiles, including air pollutants and pesticides, on DNMT3B enzyme activity, which is one of the major DNA methylation enzymes. We identified four electrophiles that reduced DNMT3B enzyme activity. Among these four candidates, we focused on 1,2-naphthoquinone (1,2-NQ), an air pollutant. The binding sites of 1,2-NQ on DNMT3B were analyzed using LC-MS/MS, and specific lysine and histidine residues were identified. Next, we examined transcriptome changes in 1,2-NQ by RNA-Seq. We found that the expression of chemokines that regulate inflammatory responses was increased. Additionally, we showed that 1,2-NQ and the DNMT inhibitor induced the expression of chemokines, including CXCL8, in a time-dependent manner. In addition, we analyzed the DNA methylation levels of CXCL8 enhancer sites using bisulfite sequencing and found that 1,2-NQ decreased its methylation levels. Moreover, we revealed that 1,2-NQ-induced chemokines promoted A549 lung cancer cell growth. Our results indicate that 1,2-NQ covalently modifies DNMT3B and induces epigenetic disorders that alter gene expression, such as chemokines that promote lung cancer proliferation.
