2-Aminobenzamide antagonizes DNA de-methylation which precedes induced differentiation of Friend erythroleukemia cells by N’-methylnicotinamide.

Abstract

Induction of Friend erythroleukemia cell (FELC) differentiation has been shown to be preceded by a genome wide hypomethylation of the DNA (1-3). Recent work suggests that DNA becomes actively de-methylated by removal of 5-methylcytosine (5-mC) and replacement with cytosine during chemically induced FELC differentiation (4,5). Nicotinamide (NA) and several of its analogs induce FELC differentiation (6-12), but inhibition of ADP-ribosylation is not required for induction. Aminobenzamides (-AB) are potent inhibitors of ADP-ribosylation with very low inducer activity which were found to inhibit induction of differentiation (10,12) by hexamethylene bisacetamide (HMBA) and dimethylsulfoxide (DMSO). In previous studies, we have shown that NA and its inducer-capable analogs cause DNA hypomethylation in cultured FELCs (11), with N’-methylnicotinamide (N’-MN) being the most potent. Subsequent work determined that up to 6% of 5-mC in the existing DNA of differentiating FELCs was removed during the first 24 hrs of N’-MN exposure (5). N’-MN has no inhibitory effect on ADP-ribose transferase activity, but causes the highest level of DNA de-methylation of any compound tested. We designed experiments using 2-AB in combination with N’-MN in cultured FELCs in order to determine if ADP-ribosylation may be involved in the process of DNA de-methylation.