The -Encoded Truncated RNase PH Protein Inhibits RNase P Maturation of Pre-tRNAs with Short Leader Sequences in the Absence of RppH.

RNase PH, encoded by the gene, is a 3'→5' exoribonuclease that in participates primarily in the 3' maturation of pre-tRNAs and the degradation of rRNA in stationary-phase cells. Interestingly, the routinely used laboratory strains of MG1655 and W3110 have naturally acquired the allele, encoding a truncated catalytically inactive RNase PH protein which is widely assumed to be benign. Contrary to this assumption, we show that the -encoded Rph-1 protein inhibits RNase P-mediated 5'-end maturation of primary pre-tRNAs with leaders of <5 nucleotides in the absence of RppH, an RNA pyrophosphohydrolase.