Phenylhexyl isothiocyanate induces gene p15 demethylation by down-regulating DNA methyltransferases in Molt-4 cells

This study is to investigate the effect of phenylhexyl isothiocyanate (PHI), which has been proved to be a novel histone deacetylase inhibitor (HDACi) recently, on gene p15 de novo expression in acute leukemia cell line Molt-4, and to further study its potential mechanism.  Modified methylation specific PCR (MSP) was used to screen p15-M and p15-U mRNA. DNA methyltransferase1 (DNMT1), 3A (DNMT3A), 3B (DNMT3B) and p15 mRNA were measured by RT-PCR.  P15 protein was detected by Western blotting.  Hypermethylation of gene p15 was reversed and activation transcription of gene p15 in Molt-4 was de novo after 5 days exposure to PHI in a concentration dependent manner.  DNMT1 and DNMT3B were inhibited by exposure to PHI for 5 days (P < 0.05).  Alteration of DNMT3A was not significant.  It is showed that PHI could reverse hypermethylation of gene p15 and transcriptional activation of gene p15 is de novo by PHI.  It may result from down-regulating DNA methyltransferases, DNMT1 and DNMT3B, or up-regulating the histone acetylation that allows chromatin unfolding and the accessibility of regulators for transcriptional activation in the p15 promoter.