Binding and biomimetic cleavage of the RNA poly(U) by synthetic polyimidazoles

Four polyimidazoles were used in the binding and cleavage studies with poly(U). The two polydisperse polyvinylimidazoles were previously described by others, while the other two new polymers of polyethyleneimines were prepared by cationic polymerization of oxazolines. The latter had imidazole units attached to each nitrogen of the polymers. They were characterized by gel permeation chromatography and had very low polydispersities. When they were partially protonated they bound to the poly(U) and catalyzed its cleavage by a process analogous to that used by the enzyme ribonuclease A. The kinetics of the cleavage were followed by an assay we had previously described using phosphodiesterase I from Crotalus venom after the cleavage processes. Cleavage of poly(U) with Zn(2+) was also examined, with and without the polymers. A scheme is described in which these cleavages could be made sequence selective with various RNAs, particularly with important targets, such as viral RNAs.