The nonstructural protein 8 (nsp8) of the SARS coronavirus interacts with its ORF6 accessory protein

Virology. 2007 Sep 30;366(2):293-303. doi: 10.1016/j.virol.2007.04.029. Epub 2007 May 25.

Abstract

Severe acute respiratory syndrome (SARS) coronavirus (SARS-CoV) caused a severe outbreak in several regions of the world in 2003. The SARS-CoV genome is predicted to contain 14 functional open reading frames (ORFs). The first ORF (1a and 1b) encodes a large polyprotein that is cleaved into nonstructural proteins (nsp). The other ORFs encode for four structural proteins (spike, membrane, nucleocapsid and envelope) as well as eight SARS-CoV-specific accessory proteins (3a, 3b, 6, 7a, 7b, 8a, 8b and 9b). In this report we have cloned the predicted nsp8 gene and the ORF6 gene of the SARS-CoV and studied their abilities to interact with each other. We expressed the two proteins as fusion proteins in the yeast two-hybrid system to demonstrate protein-protein interactions and tested the same using a yeast genetic cross. Further the strength of the interaction was measured by challenging growth of the positive interaction clones on increasing gradients of 2-amino trizole. The interaction was then verified by expressing both proteins separately in-vitro in a coupled-transcription translation system and by coimmunoprecipitation in mammalian cells. Finally, colocalization experiments were performed in SARS-CoV infected Vero E6 mammalian cells to confirm the nsp8-ORF6 interaction. To the best of our knowledge, this is the first report of the interaction between a SARS-CoV accessory protein and nsp8 and our findings suggest that ORF6 protein may play a role in virus replication.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cell Line
  • Chlorocebus aethiops
  • Cloning, Molecular
  • Cytoplasm / chemistry
  • Immunoprecipitation
  • Microscopy, Confocal
  • Microscopy, Fluorescence
  • Protein Binding
  • Severe acute respiratory syndrome-related coronavirus / metabolism*
  • Two-Hybrid System Techniques
  • Viral Nonstructural Proteins / genetics
  • Viral Nonstructural Proteins / metabolism*

Substances

  • Viral Nonstructural Proteins
  • nonstructural protein, coronavirus