InterPro domain: IPR016848

This entry represents the p29 subunit (also known as Rpp29 or Pop4) of the related ribonucleoproteins ribonuclease (RNase) P and RNase MRP from eukaryotes [ 1 ]. Rpp29 has a conserved C-terminal domain with an Sm-like fold [ 2 ]. Rpp29 ( 3.1.26.5 ) catalyses the endonucleolytic cleavage of RNA, removing 5'-extranucleotides from tRNA precursor. It interacts with the Rpp25 and Pop5 subunits.

Ribonuclease P (Rnp) is a ubiquitous ribozyme that catalyzes a Mg2 -dependent hydrolysis to remove the 5'-leader sequence of precursor tRNA (pre-tRNA) in all three domains of life [ 3 ]. In bacteria, the catalytic RNA (typically ~120kDa) is aided by a small protein cofactor (~14kDa) [ 4 ]. Archaeal and eukaryote RNase P consist of a single RNA and archaeal RNase P has four or five proteins, while eukaryotic RNase P consists of 9 or 10 proteins. Eukaryotic and archaeal RNase P RNAs cooperatively function with protein subunits in catalysis [ 5 ].

Eukaryotic nuclear RNase P shares most of its protein components with another essential RNP enzyme, nucleolar RNase MRP [ 6 ]. RNase MRP (mitochondrial RNA processing) is an rRNA processing enzyme that cleaves various RNAs, including ribosomal, messenger, and mitochondrial RNAs. It can cleave a specific site within precursor rRNA to generate the mature 5'-end of 5.8S rRNA [ 6 ]. Despite its name, the vast majority of RNase MRP is localized in the nucleolus [ 7 ]. RNase MRP has been shown to cleave primers for mitochondrial DNA replication and CLB2 mRNA. In yeast, RNase MRP possesses one putatively catalytic RNA and at least 9 protein subunits (Pop1, Pop3-Pop8, Rpp1, Snm1 and Rmp1) [ 8 ]. Human RNase MRP complex consists of 267 nucleotides and supports the interaction with and among at least seven protein components: hPop1, hPop5, Rpp20, Rpp25, Rpp30, Rpp38, and Rpp40) and three additional proteins, hPop4, Rpp21 and Rpp14, have been reported to be associated with at least a subset of RNase MRP complexes [ 9 ].

1. hPop4: a new protein subunit of the human RNase MRP and RNase P ribonucleoprotein complexes. Nucleic Acids Res. 27, 2465-72
2. Crystal structure of archaeal ribonuclease P protein aRpp29 from Archaeoglobus fulgidus. Biochemistry 43, 14128-38
3. The nucleotide sequence of chromosome I from Saccharomyces cerevisiae. Proc. Natl. Acad. Sci. U.S.A. 92, 3809-13
4. Chance and necessity in the evolution of RNase P. RNA 24, 1-5
5. Rpp14 and Rpp29, two protein subunits of human ribonuclease P. RNA 5, 153-7
6. Probing the structure of Saccharomyces cerevisiae RNase MRP. Biochem. Soc. Trans. 33, 479-81
7. Of proteins and RNA: the RNase P/MRP family. RNA 16, 1725-47
8. Accumulation of noncoding RNA due to an RNase P defect in Saccharomyces cerevisiae. RNA 17, 1441-50
9. RNase MRP and disease. Wiley Interdiscip Rev RNA 1, 102-16