Fidelity of tRNA 5′-maturation: A possible basis for the functional dependence of archaeal and eukaryal RNase P on multiple protein cofactors

Abstract

RNase P, which catalyzes tRNA 5′-maturation, typically comprises a catalytic RNase P RNA (RPR) and a varying number of RNase P proteins (RPPs): 1 in bacteria, at least 4 in archaea and 9 in eukarya. The four archaeal RPPs have eukaryotic homologs and function as heterodimers (POP5RPP30 and RPP21RPP29). By studying the archaeal Methanocaldococcus jannaschii RPR's cis cleavage of precursor tRNAGln (pre-tRNAGln), which lacks certain consensus structures/sequences needed for substrate recognition, we demonstrate that RPP21RPP29 and POP5RPP30 can rescue the RPR's mis-cleavage tendency independently by 4-fold and together by 25-fold, suggesting that they operate by distinct mechanisms. This synergistic and preferential shift toward correct cleavage results from the ability of archaeal RPPs to selectively increase the RPR's apparent rate of correct cleavage by 11140-fold, compared to only 480-fold for mis-cleavage. Moreover, POP5RPP30, like the bacterial RPP, helps normalize the RPR's rates of cleavage of non-consensus and consensus pre-tRNAs. We also show that archaeal and eukaryal RNase P, compared to their bacterial relatives, exhibit higher fidelity of 5′-maturation of pre-tRNAGln and some of its mutant derivatives. Our results suggest that protein-rich RNase P variants might have evolved to support flexibility in substrate recognition while catalyzing efficient, high-fidelity 5′-processing. © 2011 The Author(s).