Methylation of PARP-1 promoter involved in the regulation of benzene-induced decrease of PARP-1 mRNA expression.

Benzene is an established hematotoxic carcinogen which can cause leukemia. DNA damage and disorder of repair capacity are the crucial mechanisms in leukemogenesis of benzene. DNA methyltransferase inhibitor, 5-aza-2'-deoxycytidine (5-aza) and histone deacetylase inhibitor, trichostatin A (TSA) are two kinds of key epigenetic modification reagents. The mRNA expression of poly(ADP-ribose) polymerases-1 (PARP-1), a pivotal repair gene, has been decreased by benzene. However, the effect of epigenetic modification on benzene-induced low PARP-1 expression has not been reported. In this study, lymphoblastoid cell line F32 was incubated by benzene and then further treated with 5-aza and TSA, alone or in combination. The reverse transcription-polymerase chain reaction and methylation-specific PCR were performed to examine the mRNA expression and methylation status of PARP-1, respectively. Results showed a dramatic decrease of PARP-1 mRNA expression and a simultaneously obvious increase in the level of PARP-1 methylation in benzene-treated cells compared to the control. Further, the PARP-1 mRNA expression was restored and the level of PARP-1 methylation was also reduced following epigenetic inhibitors, 5-aza and TSA, alone or in combination treatments. Taken together, methylation of PARP-1 promoter might be involved in the regulation of benzene-induced decrease of PARP-1 mRNA expression.