LEAD-CATALYZED CLEAVAGE OF RIBONUCLEASE-P RNA AS A PROBE FOR INTEGRITY OF TERTIARY STRUCTURE

Pb2+-catalyzed cleavage of RNA has been shown previously to be a usefu l probe for tertiary structure. In the present study, Pb2+ cleavage pa tterns were identified for ribonuclease P RNAs from three phylogenetic ally disparate organisms, Escherichia coli, Chromatiom vinosum, Bacill us sobtilis, and for E.coli RNase P RNAs that had been altered by dele tions. Each of the native RNAs undergoes cleavage at several sites in the core structure that is common to all bacterial RNase P RNAs. Ail t he cleavages occur in non-paired regions of the secondary structure mo dels of the RNAs, in regions likely to be involved in tertiary interac tions. Two cleavage sites occur at homologous positions in all the nat ive RNAs, regardless of sequence variation, suggesting common tertiary structural features. The Pb2+ cleavage sites in four deletion mutants of E.coli RNase P RNA differed from the native pattern, indicating al terations in the tertiary structures of the mutant RNAs. This conclusi on is consistent with previously characterized properties of the mutan t RNAs. The Pb2+ cleavage assay is thus a useful probe to reveal alter ation of tertiary structure in RNase P RNA.