Eukaryotic Nuclear RNase P: Structures and Functions

Abstract

Over the past decade, ribonucleic acids (RNAs) have gained recognition as the catalysts for an increasing number of biochemical reactions. This chapter discusses the structures and functions of eukaryotic nuclear ribonuclease P (RNase P). The recognition and alignment of appropriate cleavage site proceeds through Watson–Crick base-pairing among the regions of complementary sequence within the same RNA chain. The function of RNase P in vivo is to bind and cleave all of the various transfer RNA (tRNA) precursors. To accomplish this in the absence of base-pairing, common determinants in the three-dimensional structures of the substrates become important. Because of the complex mode of substrate recognition by RNase P, the knowledge of the tertiary structures of both the catalytic and substrate RNAs as well as an understanding of the way these structured RNAs interact is necessary for the determination of its catalytic mechanism. Ribonuclease P is a ribonucleoprotein enzyme that endonucleolytically cleaves precursor-tRNA molecules, generating mature 5' termini. The enzyme RNase P is an essential, well-conserved functionally and has been found in every organism tested. Yeast is a single-cell eukaryotic organism that contains two versions of RNase P: a nuclear form that processes nuclear-encoded pre-tRNAs destined for the cytoplasm and a mitochondrial form that processes pre-tRNAs encoded by the mitochondrial genome.