Reduced RNA synthesis levels in isolated mouse liver nuclei following reaction with [(H₂O)(NH₃)5Ru(II)]²⁺

Abstract

The goal of this study is to establish the effect of [(H₂O)(NH3)5Ru(II)]²⁺ reaction of nuclei on their RNA transcription levels. This question is important because ammineruthenium compounds share chemical and biological properties with the chemotherapeutic agent cis-dichlorodiammineplatinum(II) or cisplatin. First we demonstrate that mouse liver nuclei are active in RNA transcription in vitro and characterize the optimum conditions for in vitro transcription. Synthetic rates in the presence of inhibitors actinomycin D and α-Amanitin and measurements of oligo(dT)-cellulose RNA binding levels suggest that all three RNA Polymerases are active in synthesis at about the following percentages-RNA Polymerase I(30%), II(50%) and III(20%). Mouse liver nuclei reacted with [(H₂O)(NH₃)5Ru(II)]²⁺ and then oxidized had (NH₃)₅ Ru(III)³⁺-DNA adduct levels inversely related to total RNA synthetic rates. Oligo(dT) cellulose RNA binding levels did not vary with DNA adduct density. These data suggest that direct DNA lesions rather than [(NH₃)₅Ru(III)]³⁺ effects on other aspects of the transcription system are responsible for the diminished RNA synthesis levels. Ammineruthenium complexes remain desirable candidates for chemotherapeutic agents that may be safely administered in the unreactive ruthenium(III) state and be activated toward DNA binding by reduction in the hypoxic environment of many tumour cells.