A functional role of polyADPR in DNA synthesis

Preincubation of rat liver nuclei or chromatin with NAD suppressed the incorporation of [³H]TTP into DNA which was more pronounced at 25° than at 37°. Mg²⁺ or excessive amounts of DNA polymerase added to the assay system containing chromatin did not alter the incorporation of [³H]TTP. On the other hand, when calf thymus DNA was added, the DNA polymerase activity was restored. Nicotinamide added to the preincubation medium containing chromatin blocked polyADPR synthesis and prevented the inhibition of DNA synthesis induced by NAD. The results of the present study demonstrated that preincubation of chromatin with NAD reduced its template capacity for DNA synthesis. Evidence is presented which suggests that the formation of polyADPR influences DNA synthesis.