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Evidence for an RNA-based catalytic mechanism in eukaryotic nuclear ribonuclease P

  • BRIAN C. THOMAS (a1) (a2) (a3), JOEL CHAMBERLAIN (a4) (a5), DAVID R. ENGELKE (a4) (a6) and PETER GEGENHEIMER (a1) (a2)
    • Published online: 01 April 2000

Ribonuclease P is the enzyme responsible for removing the 5′-leader segment of precursor transfer RNAs in all organisms. All eukaryotic nuclear RNase Ps are ribonucleoproteins in which multiple protein components and a single RNA species are required for activity in vitro as well as in vivo. It is not known, however, which subunits participate directly in phosphodiester-bond hydrolysis. The RNA subunit of nuclear RNase P is evolutionarily related to its catalytically active bacterial counterpart, prompting speculation that in eukaryotes the RNA may be the catalytic component. In the bacterial RNase P reaction, Mg(II) is required to coordinate the nonbridging phosphodiester oxygen(s) of the scissile bond. As a consequence, bacterial RNase P cannot cleave pre-tRNA in which the pro-RP nonbridging oxygen of the scissile bond is replaced by sulfur. In contrast, the RNase P reaction in plant chloroplasts is catalyzed by a protein enzyme whose mechanism does not involve Mg(II) coordinated by the pro-RP oxygen. To determine whether the mechanism of nuclear RNase P resembles more closely an RNA- or a protein-catalyzed reaction, we analyzed the ability of Saccharomyces cerevisiae nuclear RNase P to cleave pre-tRNA containing a sulfur substitution of the pro-RP oxygen at the cleavage site. Sulfur substitution at this position prohibits correct cleavage of pre-tRNA. Cleavage by eukaryotic RNase P thus depends on the presence of a thio-sensitive ligand to the pro-RP oxygen of the scissile bond, and is consistent with a common, RNA-based mechanism for the bacterial and eukaryal enzymes.

Corresponding author
Reprint requests to: Peter Gegenheimer, Department of Molecular Biosciences, The University of Kansas, 2045 Haworth Hall, Lawrence, Kansas 66045-2106, USA; e-mail:
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  • ISSN: 1355-8382
  • EISSN: 1469-9001
  • URL: /core/journals/rna
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