Processing of m1 RNA at the 3' end protects its primary transcript from degradation.

M1 RNA, the catalytic subunit of Escherichia coli RNase P, is an essential ribozyme that processes the 5' leader sequence of precursor tRNAs. It is generated by the removal of 36 nucleotides from the 3' end of the primary rnpB transcript (pM1 RNA), but the biological significance of this reaction in bacterial metabolism remains obscure. In this study, we constructed and analyzed bacterial strains carrying mutations in the rne-dependent site of their rnpB genes, showing that the 3' processing of M1 RNA is essential for cell viability. Furthermore, we demonstrate that pM1 RNA can undergo not only 3' processing but also poly(A)-dependent degradation. Therefore, our results suggest that the 3' processing of M1 RNA provides a functional mechanism for the protection of its primary transcript against degradation.