Inhibitory effect of calcium‐binding protein regucalcin on Ca2+‐activated DNA fragmentation in rat liver nuclei

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Abstract
Incubation of isolated rat liver nuclei with ATP, NAD+, and micromolar Ca2+ concentrations of various metal ions resulted in extensive DNA hydrolysis. Half‐maximal activity occurred with 1.0 μM Ca2+ added, and saturation of the process was observed with 10 μM Ca2+, The Ca2+ (10 μM)‐activated DNA fragmentation was inhibited by the presence of Ca2+‐binding protein regucalcin isolated from rat liver cytosol. The inhibitory effect of regucalcin was complete at 0.5 μM. At 25μM Ca2+ added, such an effect of regucalcin (1.0μM) was not seen, Regucalcin also inhibited Ca2+‐activated DNA fragmentation in the presence or calmodulin (10 and 20 μg). The results show that regucalcin can inhibit the Ca2+‐activated DNA fragmentation due to binding the metal, suggesting a role in regulation of liver nuclear functions.