Ribonuclease P: The Evolution of an Ancient RNA Enzyme

ABSTRACT

Ribonuclease P (RNase P) is an ancient and essential endonuclease that catalyses the cleavage of the 5′ leader sequence from precursor tRNAs (pre-tRNAs). The enzyme is one of only two ribozymes which can be found in all kingdoms of life (Bacteria, Archaea, and Eukarya). Most forms of RNase P are ribonucleoproteins; the bacterial enzyme possesses a single catalytic RNA and one small protein. However, in archaea and eukarya the enzyme has evolved an increasingly more complex protein composition, whilst retaining a structurally related RNA subunit. The reasons for this additional complexity are not currently understood. Furthermore, the eukaryotic RNase P has evolved into several different enzymes including a nuclear activity, organellar activities, and the evolution of a distinct but closely related enzyme, RNase MRP, which has different substrate specificities, primarily involved in ribosomal RNA biogenesis. Here we examine the relationship between the bacterial and archaeal RNase P with the eukaryotic enzyme, and summarize recent progress in characterizing the archaeal enzyme. We review current information regarding the nuclear RNase P and RNase MRP enzymes in the eukaryotes, focusing on the relationship between these enzymes by examining their composition, structure and functions.

KEYWORDS :

• RNase P
• RNase MRP
• tRNA processing
• rRNA processing
• holoenzyme
• nucleolus

Notes

¹Estimation of mass assumes a single RNA subunit and that each protein is present only once in the holoenzyme. with more found in the eukaryotic enzymes, nine proteins in yeast and ten proteins in human (∼ 70% by mass)

²Much of the sequence data for RNase P is held and maintained by J. W. Brown at North Carolina State University. The RNase P Database. http://jwbrown.mbio.ncsu.edu/RNaseP/home.html.