RNA-protein interactions in Rnase P

Abstract The endoribonuclease RNase Pis a ubiquitous and essential ribonucleoprotein. It cleaves the 5’ terminal leader sequences of precursor tRNAs (ptRNAs) to generate mature tRNAs (Figure 1). Much of our current understanding of this enzyme is derived from studies of RNase P from Escherichia coli and Bacillus subtilis (1, 2). In E. coli, RNase P consists of an RNA subunit (Ml RNA, 377 nucleotides (nt)) and a protein subunit (CS protein, 119 amino acid residues). Ml RNA and CS protein are encoded by the rnpB and rnpA genes, respectively. Apart from ptRNAs, the precursors to 4.5S RNA (p4.5S RNA) (Figure 1) and lOSa RNA (H. Inokuchi, personal communication) are also processed by RNase P from E. coli in vitro and in vivo. The observation that Ml RNA can catalyse the hydrolysis of ptRNAs in vitro even in the absence of CS protein demonstrated that RNase P owed its catalytic potential to its RNA subunit and that the protein subunit is a co-factor (3). How ever, both Ml RNA and CS protein are essential for the activity of RNase P in vivo. This latter observation emphasizes the importance of auxiliary role(s) played by the protein subunit in vivo (4, 5).