Methylation of PARP-1 promoter involved in the regulation of nano-SiO2-induced decrease of PARP-1 mRNA expression

• DOI: 10.1016/j.toxlet.2012.01.007
• Publication Date: 2012-01-14T19:30:48Z
• Authors: Chunmei Gong; Gonghua Tao; Linqing Yang; Jianjun Liu; Qingcheng Liu; Wenjie Li; Zhixiong Zhuang
• Keywords: DNA (Cytosine-5-)-Methyltransferase 1; Keratinocytes; 0301 basic medicine; Blotting, Western; Genetic Vectors; Lentivirus; Poly (ADP-Ribose) Polymerase-1; DNA Methylation; Real-Time Polymerase Chain Reaction; Gene Expression Regulation, Enzymologic; Cell Line; Epigenesis, Genetic; 3. Good health; 03 medical and health sciences; Gene Knockdown Techniques; Humans; Nanoparticles; DNA (Cytosine-5-)-Methyltransferases; RNA, Messenger; Poly(ADP-ribose) Polymerases; RNA, Small Interfering; Promoter Regions, Genetic; Plasmids

Nano silicon dioxide (nano-SiO2) is becoming more and more widely applied in the fields of industry. The potential toxic effects of nano-SiO2 and its hazard to human health are drawing more attention. The mRNA expression of poly(ADP-ribose) polymerases-1(PARP-1), a pivotal repair gene, has been decreased by nano-SiO2 exposure. However, the effect of epigenetic modification on nano-SiO2-induced low PARP-1 expression has not been reported. In this study, HaCaT cells with or without DNA methyltransferase 1(DNMT1) knock down were incubated with nano-SiO2 and then further treated with DNMT inhibitor, 5-aza-2-deoxycytidine (DAC), which is a kind of key epigenetic modification reagents. Real-time Q-PCR and western blotting were used to examine the mRNA and protein expression of PARP-1. For promoter methylation status of PARP-1, methylation-specific PCR (MSP) and Bisulfite sequencing assay were performed. Results showed a dramatic decrease of PARP-1 expression on mRNA and protein level and a simultaneously obvious increase in the level of PARP-1 methylation in nano-SiO2-treated cells compared to the control group. Further, the expression and promoter methylation of PARP-1 in HaCaT cells were restored following DNMT1 knock down, suggesting that the effects of PARP-1 promoter hypermethylation are mediated at least in part by DNMT1. Taken together, methylation of PARP-1 promoter might be involved in the regulation of nano-SiO2-induced decrease of PARP-1 expression.