Objective  To investigate the effects of different doses of sodium arsenite (NaAsO₂) on mRNA transcription of N-methylpurine-DNA glycosylase (MPG), poly (adenosine diphosphate-ribose) polymerase 1 (PARP1), and x-ray repair cross-complementing 1 (XRCC1) gene and its modification on H4K20me1 of promoter region and coding region in human keratinocyte (HaCaT) cells.

  Methods  HaCaT cells were treated with 2.50, 5.00, 10.00 μmol/L NaAsO₂ for 24 hours and a blank control group without NaAsO₂ treatment was established. Quantitative real-time polymerase chain reaction was used to detect mRNA expressions of MPG, PARP1, and XRCC1 gene. Quantitative chromatin immuno-precipitation was adopted to determine the level of H4K20me1 modifications in the promoter region (CHIP1 and CHIP2) and coding region (CHIP3 and CHIP4) of MPG, PARP1, XRCC1 gene.

  Results  The mRNA levels of MPG, PARP1, and XRCC1 gene were not significantly different from those of the control group at the NaAsO₂ dosage of 2.5 μmol/L (P > 0.05) but the levels gradually decreased significantly at the dosages of 5.00 and 10.00 μmol/L (both P < 0.05). Compared with those of the control group, the enrichments of H4K20me1 in CHIP1 and CHIP2 regions of MPG promoter gene and CHIP2 regions of promoter PARP1 gene in all NaAsO₂ dosage groups were not significantly different (P > 0.05); while, the enrichments of H4K20me1 in CHIP1 and CHIP2 regions of XRCC1 promoter gene and CHIP1 regions of PARP1 promoter gene in 5.00 and 10.00 μmol/L dosage groups were reduced significantly (P < 0.05 for all); the enrichment of H4K20me1 in CHIP3 and CHIP4 regions of MPG, PARP1, XRCC1 coding gene were also reduced significantly for the 5.00 and 10.00 μmol/L dosage groups (all P < 0.05).

  Conclusion  NaAsO₂ could decrease the mRNA transcription level of MPG, PARP1 and XRCC1 genes by inhibiting the level of H4K20me1 of PARP1, XRCC1 gene promoter region and MPG, PARP1, XRCC1 gene coding region in HaCaT cells.