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 formation 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.