ADP-ribosylation of chromosomal proteins and mouse mammary tumor virus gene expression. Glucocorticoids rapidly decrease endogenous ADP-ribosylation of nonhistone high mobility group 14 and 17 proteins.

The relationship between endogenous ADP-ribosylation of chromosomal proteins and glucocorticoid-regulated mouse mammary tumor virus gene expression was investigated in cultured mouse mammary tumor cells. It was observed that glucocorticoids quickly decreased endogenous (ADP-ribose)n on the nonhistone high mobility group (HMG) 14 and 17 proteins. The half-time for this loss was 8 and 17 min, respectively, for the two proteins. (ADP-ribose)n on HMG 1 and 2 and on histone H1 was less susceptible to hydrolysis during glucocorticoid treatment. The rapid loss of (ADP-ribose)n from HMG 14 and 17 occurred in the same time frame as the induction of mouse mammary tumor virus RNA synthesis by glucocorticoids in these cells (Young, H. A., Shih, T. Y., Scolnick, E. M., and Parks, W. P. (1977) J. Virol. 21, 139-149). 3-Amino-benzamide, a specific inhibitor of (ADP-ribose)n synthetase, increased mouse mammary tumor virus RNA levels with an accompanying decrease in endogenous ADP-ribosylation of HMG 14 and 17. These results show that a decrease in endogenous ADP-ribosylation of HMG 14 and 17 is a consequence of glucocorticoid action and suggest that loss of (ADP-ribose)n from these proteins may be an important event in mouse mammary tumor virus gene expression.