Pop3p is essential for the activity of the RNase MRP and RNase P ribonucleoproteins in vivo

EMBO J. 1997 Jan 15;16(2):417-29. doi: 10.1093/emboj/16.2.417.


RNase MRP is a ribonucleoprotein (RNP) particle which is involved in the processing of pre-rRNA at site A3 in internal transcribed spacer 1. Although RNase MRP has been analysed functionally, the structure and composition of the particle are not well characterized. A genetic screen for mutants which are synthetically lethal (sl) with a temperature-sensitive (ts) mutation in the RNA component of RNase MRP (rrp2-1) identified an essential gene, POP3, which encodes a basic protein of 22.6 kDa predicted molecular weight. Over-expression of Pop3p fully suppresses the ts growth phenotype of the rrp2-1 allele at 34 degrees C and gives partial suppression at 37 degrees C. Depletion of Pop3p in vivo results in a phenotype characteristic of the loss of RNase MRP activity; A3 cleavage is inhibited, leading to under-accumulation of the short form of the 5.8S rRNA (5.8S(S)) and formation of an aberrant 5.8S rRNA precursor which is 5'-extended to site A2. Pop3p depletion also inhibits pre-tRNA processing; tRNA primary transcripts accumulate, as well as spliced but 5'- and 3'-unprocessed pre-tRNAs. The Pop3p depletion phenotype resembles those previously described for mutations in components of RNase MRP and RNase P (rrp2-1, rpr1-1 and pop1-1). Immunoprecipitation of epitope-tagged Pop3p co-precipitates the RNA components of both RNase MRP and RNase P. Pop3p is, therefore, a common component of both RNPs and is required for their enzymatic functions in vivo. The ubiquitous RNase P RNP, which has a single protein component in Bacteria and Archaea, requires at least two protein subunits for its function in eukaryotic cells.

MeSH terms

  • Alleles
  • Cell Survival
  • Cloning, Molecular
  • DNA, Fungal / chemistry
  • Electrophoresis, Polyacrylamide Gel
  • Endoribonucleases / metabolism*
  • Molecular Sequence Data
  • Molecular Weight
  • Mutagenesis
  • Phenotype
  • RNA Splicing
  • RNA, Bacterial / metabolism*
  • RNA, Catalytic / metabolism*
  • RNA, Fungal / metabolism
  • Ribonuclease P
  • Ribonucleoproteins / metabolism*
  • Saccharomyces cerevisiae
  • Temperature


  • DNA, Fungal
  • RNA, Bacterial
  • RNA, Catalytic
  • RNA, Fungal
  • Ribonucleoproteins
  • Endoribonucleases
  • mitochondrial RNA-processing endoribonuclease
  • Ribonuclease P

Associated data

  • GENBANK/X95844