Reduction of Mono(ADP-ribosyl)ation of Histones in Rat Testis by Gonadotropin-Testosterone System

Mono(ADP-ribose) synthetase activity in the nuclear fraction of immature rat testis was investigated in reference to the effect of testosterone. When the nuclear fraction was incubated with [ 32P] NAD in the presence of nicotinamide, an inhibitor of poly (ADP-ribose) synthetase, some proteins with a molecular mass of 14.4∼21.5 kDa were ADP-ribosylated. In these proteins, H2B and H3 histones were found by sequencing 20 amino acids in the N-terminus. Their incorporations of ADP-ribose moiety were significantly decreased in immature rats at 4 hr after the subcutaneous injection of testosterone. Furthermore, the treatments with LH and FSH of the immature rats reduced mono(ADP-ribosyl)ations of H2B and H3 histones in a time-dependent manner. These results suggest that the testicular mono(ADP-ribose) synthetase activity is under the control of gonadotropin-testosterone system and is possibly related to differentiation of the testis.