Previous suggestions of CpG-specific apoptotic commitment implied critical
epigenetic modulation of house-keeping genes which have canonical CpG islan
ds at 5' promoter regions. Differential housekeeping gene activity however
has not been shown. Using a focussed microarray (genechip) of 22 housekeepi
ng genes we show this in apoptosis induced in human Chang liver cells by DC
NP (2,6-dichloro-4-nitrophenol), a non-genotoxic inhibitor of sulfate detox
ification. 3-7 folds downregulation of 9 genes in glycolysis, tricarboxylic
acid cycle and the respiratory electron transport chain suggested gene-dir
ected energy depletion which was correlated with observed ATP depletion. 4
folds downregulation of the pyruvate dehydrogenease gene suggested gene-dir
ected metabolic acidosis which was correlated with observed cell acidificat
ion. Other differential housekeeping gene activity, including 4 folds upreg
ulation of microtubular alpha-tubulin gene, and 2 folds upregulation of ubi
quitin, also had a bearing on apoptosis. Broadspectrum zVAD-fmk caspase inh
ibition abolished 200 bp DNA ladder fragmentations but not the CpG-specific
megabase fragmentations and other hallmarks of cell destruction, suggestin
g a caspase-independent cell death. Death appeared committed at gene-level.