Endogenous ADP Ribosylation of High Mobility Group Proteins 1 and 2 and Histone H1 Following DNA Damage in Intact Cells

Endogenous ADP ribosylation of nonhistone high-mobility group (HMG) proteins and histone H1 was studied in cultured mouse mammary tumor cells following treatment with N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). MNNG treatment of cells caused a rapid and transient increase in ADP ribosylation of histone H1 and HMG 1 and 2, whereas (ADP-ribose)n on HMG 14 and 17 was not affected. 3-Aminobenzamide, an inhibitor of (ADP-ribose)n synthetase, prevented the increase in ADP ribosylation of histone H1 and HMG 1 and 2. This inhibitor enhanced the cell-killing effect of MNNG, but had no significant effect on the removal of methylated purines. The preferential increase in ADP ribosylation of HMG 1 and 2 and histone H1 may be necessary for cell recovery from DNA damage.