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Eukaryotic RNase P RNA mediates cleavage in the absence of protein

Kikovska, Ema, Svärd, Staffan G., Kirsebom, Leif A.
Proceedings of the National Academy of Sciences of the United States of America 2007 v.104 no.7 pp. 2062-2067
Giardia lamblia, RNA precursors, catalytic activity, eukaryotic cells, evolution, humans, protein subunits, ribonucleases, ribonucleoproteins, transfer RNA
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 (kobs) was five to six orders of magnitude lower, whereas the affinity for the substrate (appKd) was reduced [almost equal to]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.