Control of the position of RNase P-mediated transfer RNA precursor processing

Two Bacillus subtilis tRNA^His precursors (Green, C. J., and Vold, B. S. (1988) J. Biol. Chem. 263, 652-657) were processed by Escherichia coli RNase P in the presence of varying [Mg²⁺]. The wild type precursor was processed under all conditions to afford a single tRNA product containing 8 base pairs in the acceptor stem. In contrast, the position of processing of a mutant tRNA^His precursor (containing a G²⁷ ↔ A²⁷ alteration) was shown to be condition-dependent. Processing occurred at A²⁷ under conditions consistent with forma-tion of an A²⁷-C¹⁰⁰ base pair in the acceptor stem but at G²⁸ under conditions that disfavored base pair formation. The ability to control the site of RNase P-mediated tRNA precursor processing is unprecedented and permits analysis of the chemical factors that promote processing.