Poly(adenosine diphosphate ribose) synthesis during the cell cycle of transformed hamster lung cells.

Abstract

Summary Poly(adenosine diphosphate ribose) synthesis from 3 H-labeled nicotinamide adenine dinucleotide during the cell cycle of highly synchronized, transformed hamster lung cells was studied by autoradiography and enzymatic assay. In the G 2 phase, 70% of the cells were labeled and the average grain number was 69 per nucleus. In the M and late-S phases, only 5 and 12%, respectively, of the cells were labeled. There was a second peak of incorporation of radioactivity in the G 1 phase, in which 31% of the cells were labeled. Enzymatic assay showed that the specific activity of poly(adenosine diphosphate ribose) polymerase of isolated nuclei was highest in the G 2 phase and lowest in the S phase. In telophase, silver grains were localized exclusively over the cytoplasm and no grains were observed over the nuclei, while silver grains were localized only over the nuclei in the G 1 and G 2 phases.