Journal of Biomedical Science

, Volume 14, Issue 4, pp 523–532

The PNPase, exosome and RNA helicases as the building components of evolutionarily-conserved RNA degradation machines

Open Access

DOI: 10.1007/s11373-007-9178-y

Cite this article as:
Lin-Chao, S., Chiou, NT. & Schuster, G. J Biomed Sci (2007) 14: 523. doi:10.1007/s11373-007-9178-y


The structure and function of polynucleotide phosphorylase (PNPase) and the exosome, as well as their associated RNA-helicases proteins, are described in the light of recent studies. The picture raised is of an evolutionarily conserved RNA-degradation machine which exonucleolytically degrades RNA from 3′ to 5′. In prokaryotes and in eukaryotic organelles, a trimeric complex of PNPase forms a circular doughnut-shaped structure, in which the phosphorolysis catalytic sites are buried inside the barrel-shaped complex, while the RNA binding domains create a pore where RNA enters, reminiscent of the protein degrading complex, the proteasome. In some archaea and in the eukaryotes, several different proteins form a similar circle-shaped complex, the exosome, that is responsible for 3′ to 5′ exonucleolytic degradation of RNA as part of the processing, quality control, and general RNA degradation process. Both PNPase in prokaryotes and the exosome in eukaryotes are found in association with protein complexes that notably include RNA helicase.


RNase PH PNPase Exosome RNA helicase RNA degradation RNA polyadenylation 
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© National Science Council Taipei 2007

Authors and Affiliations

  1. 1.Institute of Molecular BiologyAcademia SinicaTaipeiTaiwan
  2. 2.Department of BiologyTechnion – Israel Institute of TechnologyHaifaIsrael

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