HISTONE HYPERACETYLATING AGENTS STIMULATE PROMOTER ACTIVITY OF HUMAN CHOLINE-ACETYLTRANSFERASE GENE IN TRANSFECTION EXPERIMENT

Butyrate (5 mM), Trichostatin A (1 mu M) or Trapoxin A (30 nM) increas ed choline acetyltransferase (ChAT) activity in cultured rat sympathet ic neurons 3- to 8-fold in 2 days. On the contrary, the three drugs de creased ChAT activity in human CHP126 cells. Butyrate had little effec t on ChAT mRNA level in these cells, suggesting post-transcriptional m echanisms for the decrease in ChAT activity. However, transient transf ection experiments using CHP126 cells revealed that the M promoter, bu t not the R promoter, of human ChAT gene was activated 20- to 130-fold by the three hyperacetylating agents. A butyrate-responsive element w as localized in the 1 kbp region upstream of exon M. Constructs contai ning in addition the genomic segment between exons M and 1 displayed m aximal basal activity and inducibility by butyrate, suggesting the pre sence of butyrate-activated promoter/enhancer elements in this region. The stimulatory effects of butyrate and Trichostatin A were also obse rved in stably transfected CHP126 clones, suggesting that the chromati n environment was not preventing the induction of the endogenous ChAT gene by butyrate, Rather, the data suggest different chromatin organiz ations for the stable transgene and the endogenous ChAT gene.