RNase 8, a novel RNase A superfamily ribonuclease expressed uniquely in placenta

Nucleic Acids Res. 2002 Mar 1;30(5):1169-75. doi: 10.1093/nar/30.5.1169.


We report the identification and characterization of the gene encoding the eighth and final human ribonuclease (RNase) of the highly diversified RNase A superfamily. The RNase 8 gene is linked to seven other RNase A superfamily genes on chromosome 14. It is expressed prominently in the placenta, but is not detected in any other tissues examined. Phylogenetic analysis suggests that RNase 7 is the closest relative of RNase 8 and that the pair likely resulted from a recent gene duplication event in primates. Further analysis reveals that the RNase 8 gene has incorporated non-silent mutations at an elevated rate (1.3 x 10(-9) substitutions/site/year) and that orthologous RNase 8 genes from 6 of 10 primate species examined have been deactivated by frameshifting deletions or point mutations at crucial structural or catalytic residues. The ribonucleolytic activity of recombinant human RNase 8 is among the lowest of members of this superfamily and it exhibits neither antiviral nor antibacterial activities characteristic of some other RNase A ribonucleases. The rapid evolution, species-limited deactivation and tissue-specific expression of RNase 8 suggest a unique physiological function and reiterates the evolutionary plasticity of the RNase A superfamily.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Base Sequence
  • Humans
  • Molecular Sequence Data
  • Organ Specificity
  • Phylogeny
  • Placenta / enzymology*
  • Pregnancy Proteins / biosynthesis*
  • Pregnancy Proteins / genetics*
  • Pregnancy Proteins / physiology
  • Primates
  • RNA, Messenger / biosynthesis
  • Ribonucleases / biosynthesis*
  • Ribonucleases / genetics*
  • Ribonucleases / physiology
  • Sequence Homology, Amino Acid
  • Sequence Homology, Nucleic Acid
  • Tissue Distribution


  • Pregnancy Proteins
  • RNA, Messenger
  • Ribonucleases
  • RNASE8 protein, human

Associated data

  • GENBANK/AF473854
  • GENBANK/AF473855
  • GENBANK/AF473856
  • GENBANK/AF473857
  • GENBANK/AF473858
  • GENBANK/AF473859
  • GENBANK/AF473860
  • GENBANK/AF473861
  • GENBANK/AF473862
  • GENBANK/AF473863