Evidence of a regulatory role of the level of poly (ADP-ribose) in chromosomal proteins in metallothionein gene expression by glucocorticoids but not by heavy metals.

The induction capacity of dexamethasone, a synthetic glucocorticoid, for the synthesis of metallothionein was about the same as that of 3-aminobenzamide, which is an inhibitor of ADP-ribosylation of chromosomal proteins, in cultured mouse mammary tumor cells. Both inductions of metallothionein were temporally correlated with a decrease in the amount of endogenous poly (ADP-ribose) on nonhistone high-mobility-group 14 and 17 proteins. In contrast, the extent of cadmium-induced metallothionein synthesis was 2-3-times that of dexamethasone or 3-aminobenzamide. However, cadmium had essentially no effect on de-ADP-ribosylation of these proteins.