, Volume 12, Issue 3, pp 147-159

Poly ADP-ribosylation of DNA-dependent RNA polymerase I from quail oviduct. Dependence on progesterone stimulation.

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Progesterone causes in goblet cells of oviducts of estrogen hormone-stimulated immature quails selectively gene activation without affecting DNA synthesis. This biological model has been used to study the influence of poly ADP-ribosylation during the processes of DNA transcription.

Administration of progesteronein vivo causes an increase of the activity of RNA polymerase I and II in isolated nuclei. This increase is accompanied by a marked decrease of the specific activity of poly (ADP-Rib) polymerase.

Afterin vitro ADP-ribosylation of nuclear proteins the template capacity of chromatin for “exogenous” RNA synthesis (withE. coli DNA-dependent RNA polymerase) as well as for “endogenous” RNA synthesis with DNA-dependent RNA polymerase II is not affected, whereas the data presented seem to indicate that the capacity for RNA synthesis mediated by “endogenous” DNA-dependent RNA polymerase I might be inhibited after ADP-ribosylation.

Evidence is presented to show that a considerable amount of poly (ADP-Rib), synthesized by poly (ADP-Rib) polymerase in isolated nuclei, is linked with RNA polymerase I. The rate of synthesis of poly (ADP-Rib) is dependent on the incubation temperature (optimum at 25°C) and it can be inhibited by the specific inhibitors of poly (ADP-Rib) polymerase nicotineamide, thymidine and formycin B. Poly (ADP-Rib) is probably associated with RNA polymerase I through a covalent linkage. ADP-ribosylated RNA polymerase I has been purified 550 fold with respect to the nuclear extract, corresponding to a 4,000 fold purification from the whole cell homogenate. The ratio between poly (ADP-Rib), formed during preincubation of nuclei with NAD, and RNA polymerase I remains almost constant during the purification procedures.

The extent of ADP-ribosylation of RNA polymerase I decreases during gene expression. Thus we conclude that poly ADP-ribosylation of this enzyme is one of the regulatory mechanisms by which specificity of DNA transcription is achieved.