DNA methylation serves as a molecular memory for gene silencing

In this recent manuscript from JP Issa's group, DNA methylation of a CMV promoter driving GFP was examined - histone deacetylase inhibitors were able to reactivate the promoter, leading to GFP expression; however the promoter remained methylated.  The inhibitors were effective for approximately two weeks, after which time the promoter became silent once again.  Treatment with inhibitors of DNA methylation however, were able to induce permanent activation of the gene.  These findings suggest that if this scenario is relevant to other promoters, it will be necessary to target DNA methylation when designing novel treatments as HDAC inhibitors are only able to temporarily "reset" chromatin.  click here to read it for yourself.