Eukaryotic RNase P RNA mediates cleavage in the absence of protein

Abstract

The universally conserved ribonucleoprotein RNase P is involved in the processing of tRNA precursor transcripts. RNase P consists of one RNA and, depending on its origin, a variable number of protein subunits. Catalytic activity of the RNA moiety so far has been demonstrated only for bacterial and some archaeal RNase P RNAs but not for their eukaryotic counterparts. Here, we show that RNase P RNAs from humans and the lower eukaryote Giardia lamblia mediate cleavage of four tRNA precursors and a model RNA hairpin loop substrate in the absence of protein. Compared with bacterial RNase P RNA, the rate of cleavage ( k obs ) was five to six orders of magnitude lower, whereas the affinity for the substrate (app K d ) was reduced ≈20- to 50-fold. We conclude that the RNA-based catalytic activity of RNase P has been preserved during evolution. This finding opens previously undescribed ways to study the role of the different proteins subunits of eukaryotic RNase P.

Ribonucleases P/MRP and the Expanding Ribonucleoprotein World

“…Universally, the RNA subunit is able to independently perform catalysis (49)(50)(51) although its enzymatic activity is greatly enhanced in the presence of the protein subunits. By inference, it is assumed that the RNA subunit of MRP is also responsible for catalysis (13).…”

Solution structure of RNase P RNA

“…In archaeal and eucaryal RNase P, additional proteins unrelated to the bacterial protein are present and correlate with a decrease in the size and structural complexity of the RNA moiety (Evans et al 2006;Ellis and Brown 2009). The specific functions of the protein components of RNase P remain subjects for debate (Marvin and Engelke 2009;Esakova and Krasilnikov 2010), but the role of the RNA is clearly catalytic: The RNase P RNA components from all three domains of life are evolutionary homologs and can catalyze tRNA maturation in vitro independently of protein cofactors (Guerrier-Takada et al 1983;Pannucci et al 1999;Kikovska et al 2007). …”

Crystal Structure and Functional Analysis of an Archaeal Chromatin Protein Alba from the Hyperthermophilic ArchaeonPyrococcus horikoshiiOT3

“…13) Eubacterial RNase P is composed of a catalytic RNA and a single protein subunit, 14) while eukaryotic RNase Ps comprise a single RNA moiety and as many as 10 proteins; a highly purified nuclear RNase P from HeLa cells has at least 10 distinct protein subunits, termed Rpp14, Rpp20, Rpp21, Rpp25, Rpp29, Rpp30, Rpp38, Rpp40, hPop1, and hPop5. [15][16][17] Although Rpp21 and Rpp29 are known to be strongly involved in the catalytic activity of human RNase P, 18) the functional roles of other human RNase P proteins in RNase P have not been established. It was reported recently that Rpp20 and Rpp25, belonging to the Alba protein family, bind to each other, and that heterodimerization regulates their RNA-binding activity, subcellular localization, and expression, though their catalytic contribution to human RNase P remains unclear.…”