Circ_0089282 inhibits carbon black nanoparticle-induced DNA damage by promoting DNA repair protein in the lung

Inhalation of carbon black nanoparticles (CBNPs) can impair lung tissue and cause DNA damage, but the epigenetic mechanism responsible for these effects is still unclear. We explored the role of circular RNAs (circRNAs) in DNA damage induced by CBNPs in the lung. Human bronchial epithelial cell lines (16HBE and BEAS-2B) were treated with 0, 5, 10, 20, 40, or 80 μg/ml CBNPs for 24, 48, and 72 h, and BALB/c mice were exposed to 8 and 80 μg/d CBNPs for 14 days to establish in vitro and vivo models of CBNP exposure, respectively. We found that CBNPs caused DNA double-strand breaks in the lung. Using high-throughput sequencing and quantitative real-time PCR to identify CBNP-related circRNAs, we identified a novel circRNA (circ_0089282) that was overexpressed in the CBNP-exposed group. We used gain-/loss-of-function approaches, RNA pulldown assays, and silver staining to explore the regulatory function of circ_0089282 and its interactions with targeted proteins. We found that circ_0089282 interference could increase CBNP-induced DNA damage, whereas overexpression resulted in the opposite. Circ_0089282 could directly bind to the fused in sarcoma (FUS) protein and positively regulate downstream DNA repair protein DNA ligase 4 (LIG4) through FUS. This regulatory effect of circRNA on DNA damage via promotion of LIG4 illustrated the interactions between genetics and epigenetics in toxicology.