RNase P is a ubiquitous ribonucleoprotein enzyme primarily responsible for cleaving the 5' leader sequence during maturation of tRNAs in all three domains of life. In bacteria, the catalytic RNA (typically ~120kDa) is aided by a small protein cofactor (~14kDa), while eukaryotic RNase P is a large RNP complex containing at least nine protein components [ (PUBMED:28971852) ].
Eukaryotic nuclear RNase P shares most of its protein components with another essential RNP enzyme, nucleolar RNase MRP [ (PUBMED:28971852) ]. RNase MRP (mitochondrial RNA processing) is an rRNA processing enzyme that cleaves a specific site within precursor rRNA to generate the mature 5'-end of 5.8S rRNA [ (PUBMED:15916546) ]. Despite its name, the vast majority of RNase MRP is localized in the nucleolus [ (PUBMED:20627997) ]. 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) [ (PUBMED:21665995) ].
This entry includes p29 subunit (also known as Rpp29 or Pop4) of the Ribonuclease P complex [ (PUBMED:10352175) ]. Its homologues from eukaryotes are also a subunit of the RNase MRP complex. The structure of the RNase P subunit, Rpp29, from Methanobacterium thermoautotrophicum has been determined. Mth Rpp29 is a member of the oligonucleotide/oligosaccharide binding fold family. It contains a structured beta-barrel core and unstructured N- and C-terminal extensions bearing several highly conserved amino acid residues that could be involved in RNA contacts in the protein-RNA complex [ (PUBMED:14673079) ]. Rpp29 ( EC 3.1.26.5 ) catalyses the endonucleolytic cleavage of RNA, removing 5'-extranucleotides from tRNA precursor. It interacts with the Rpp25 and Pop5 subunits.
hPop4: a new protein subunit of the human RNase MRP and RNase P ribonucleoprotein complexes.
Nucleic Acids Res. 1999; 27: 2465-72
Display abstract
RNase MRP is a ribonucleoprotein particle involved in the processing of pre-rRNA. The RNase MRP particle is structurally highly related to the RNase P particle, which is involved in pre-tRNA processing. Their RNA components fold into a similar secondary structure and they share several protein subunits. We have identified and characterised human and mouse cDNAs that encode proteins homologous to yPop4p, a protein subunit of both the yeast RNase MRP and RNase P complexes. The human Pop4 cDNA encodes a highly basic protein of 220 amino acids. Transfection experiments with epitope-tagged hPop4 protein indicated that hPop4 is localised in the nucleus and accumulates in the nucleolus. Immunoprecipitation assays using extracts from transfected cells expressing epitope-tagged hPop4 revealed that this protein is associated with both the human RNase MRP and RNase P particles. Polyclonal rabbit antibodies raised against recombinant hPop4 recognised a 30 kDa protein in total HeLa cell extracts and specifically co-immunoprecipitated the RNA components of the RNase MRP and RNase P complexes. Finally we showed that anti-hPop4 immunoprecipitates possess RNase P enzymatic activity. Taken together, these data show that we have identified a protein that represents the human counterpart of the yeast Pop4p protein.
We have isolated suppressors of the temperature-sensitive rRNA processing mutation rrp2-2 in Saccharomyces cerevisiae. A class of extragenic suppressors was mapped to the YBR257w reading frame in the right arm of Chromosome II. Characterization of this gene, renamed POP4, shows that the gene product is necessary both for normal 5.8S rRNA processing and for processing of tRNA. Immunoprecipitation studies indicate that Pop4p is associated with both RNase MRP and RNase P. The protein is also required for accumulation of RNA from each of the two ribonucleoprotein particles.
