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hPop4: a new protein subunit of the human RNase MRP and RNase P ribonucleoprotein complexes.


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.

Pubmed ID: 10352175


  • van Eenennaam H
  • Pruijn GJ
  • van Venrooij WJ


Nucleic acids research

Publication Data

June 15, 1999

Associated Grants


Mesh Terms

  • Amino Acid Sequence
  • Animals
  • Antibodies
  • Cell Nucleolus
  • Cloning, Molecular
  • DNA, Complementary
  • Endoribonucleases
  • HeLa Cells
  • Humans
  • Mice
  • Molecular Sequence Data
  • Precipitin Tests
  • RNA, Catalytic
  • Ribonuclease P
  • Ribonucleoproteins
  • Sequence Homology, Amino Acid