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OBJECTIVE Poly(ADP-ribosyl) ation regulates chromatin structure and transcription driving epigenetic events.We provided evidence that poly(ADP-ribose) polymerases (PARP1) is able to directly influence DNA methylation patterns in cells treated with BaP.Poly(ADP-ribose) glycohydrolase (PARG) is the primary enzyme responsible for the degradation of poly(ADP-ribose).PARG participates in a number of biological processes.Accumulating data suggest that inhibitors of PARG are potent anticancer drug candidates.The present study was designed to investigate whether inhibition of PARG would control and/or protect the DNA methylation pattern in cells.METHODS DNA methylation and DNMTs expressions were studied in detail using PARG-deficient human bronchial epithelial cell line (shPARG cell) as an in vitro model after BaP treatment using 5-mC Immunofluorescent detection, global DNA methylation assay, flow cytometric analysis, western blotting, real-time polymerase chain reaction and enzymatic activity assays.The global DNA methylation levels were determined using the EpiQuikTM DNA Methyltransferase Activity kit according to the manufacturers instructions.RESULTS Our study shows: (1) Treatment of 16HBE cells with BaP was resulted in reduction in the levels of global DNA methylation in a concentration-dependent manner.And we found that the levels of global DNA methylation in 16HBE cells were significantly reduced (P < 0.05) after 72 h of treatment with BaP than the treatment of cells with BaP for 24 h.At the same time point, no dramatic changes in global DNA methylation were observed in shPARG cell between BaP treatment for 24 h and 72 h (P >0.05).(2) Cells were treated with various concentrations of BaP for 72 h, then harvested and washed with PBS for 3 times.We found that BaP decreased DNMTs activity in 16HBE cells, and the effect of BaP was concentration dependent.However, DNMTs activity in shPARG cells did not alter significantly after BaP treatment (P>0.05).This data indicates that the DNMTs activity can be effect by PARG.(3) After cells treated with various concentrations of BaP for 72 h, we found that treatment of 16HBE cells with BaP decreased themRNA level of DNMT1, whereas increased the level of DNMT3b and MBD2, but did not change the mRNA level of DNMT3a.In contrast, treatment of shPARG cells with BaP decreased the mRNA level of DNMT3a but did not alter the level of DNMT1, but the mRNA levels of DNMT3b and MBD2 were significantly increased (P<0.05).The increase in mRNA expression of DNMT3b and MBD2 in 16HBE cells were greater than shPARG cells.Similar to mRNA expression, protein reactivation levels were also determined using western blot analysis.There was also an increase in protein expression levels of DNMT3b and MBD2 after the treatment of cells with BaP for 72 h, and the increase of the protein expression was greater in 16HBE cells than shPARG cells.BaP treatment decreased the protein expression levels of DNMT1 in the 16HBE cell, whereas BaP treatment decreased the protein expression levels of DNMT3a in shPARG cells, in a concentration-dependent manner.CONCLUSION In conclusion, our results showed that poly(ADP-ribose) glycohydrolase correlates with DNMTs and involves in regulating global DNA methylation, which would help to elucidate the underling molecular mechanism of the role of PARG during DNA methylation, and may have important implications for epigenetic therapy.