Ribonuclease P

Abstract

The gene coding for the RNA subunit of ribonuclease P (RNase P) is essential in all free-living organisms. The RNA subunit, itself, is an enzyme and, from its evolutionary tree, we can infer that it is a very ancient molecule. The specificity of this enzyme is that it cleaves other RNA molecules at the junction of single-stranded and the 5' end of double-stranded regions of RNA. One can speculate that this molecule was very useful in an ancient world in cleaving long pieces of RNA, which must have contained hairpin regions in it, into shorter molecules with the capability of different functions from the longer parent. Today, the specificity of the enzyme can be used in designing drug therapies.

Figure 1.

A summary of the catalytic properties of the RNase P RNA subunit (RPR) in three domains of life [–3]. RPP, RNase P protein subunit. Courtesy of Dr V. Gopalan, Ohio State University. Source: Guerrier-Takada et al. [1], Pannucci et al. [2] and Kikovska et al. [3].

Figure 2.

A summary of the protein subunits of RNase P from three different domains of life. Courtesy of Dr V. Gopalan, Ohio State University.

Figure 3.

A cladogram of RNase P. LUCA, last universal common ancestor. Courtesy of Dr Venkat Gopalan, Ohio State University and reprinted by permission from Lai et al. [7].

Figure 4.

Two-dimensional representation of the precursor to the amber suppressor of tRNA^Tyr from Escherichia coli. The arrow indicates the cleavage site of RNase P.

Figure 5.

Different substrates for RNase P from (a–d) E. coli and (e) Salmonella typhimurium. (a) Precursor to a tRNA. (b) Precursor to 4.5S RNA. (c) Precursor to tmRNA. (d) Precursor to a phage RNA. (e) An mRNA substrate.

Figure 6.

Operon RNAs from E. coli that are substrates for RNase P.

Figure 7.

The lac operon mRNA. (a) Schematic of the genetic system. (b) The region between the lacA and lacY genes. P and arrow indicate RNase P cleavage. (c) Results of assay in vitro of a region of lac mRNA showing cleavage by RNase P.

Figure 8.

A scheme for the early evolution of RNase P RNA. (a) Long RNA and ancient RNA subunit of RNase P (ur-M1). (b) Cleavage of the long RNA by ur-M1. (c) Further evolution of tRNA and RNA protein complexes to RNase P and RNase MRP (d₁ and d₂).

Figure 9.

Summary of the EGS scheme. (a) A precursor tRNA. (b) Reduced structure with the left-hand molecule any RNA, or mRNA, inside a cell and the right-hand molecule an EGS.

Figure 10.

Diagram of a basic peptide covalently linked to a morpholino oligonucleotide (PMO). The base sequence of the oligonucleotide can be chosen as appropriate for a particular experiment. Courtesy of AVI BioPharma, Bothell, WA, USA.