The Bunyamwera virus nonstructural protein NSs inhibits viral RNA synthesis in a minireplicon system

Virology. 2001 Mar 1;281(1):67-74. doi: 10.1006/viro.2000.0774.


The small (S) genomic segment of Bunyamwera virus (family Bunyaviridae, genus Bunyavirus) encodes the nucleocapsid protein, N, and a nonstructural protein, NSs, in overlapping reading frames. In order to elucidate the function of NSs, we established a plasmid-based minireplicon system using mammalian cells that express large amounts of T7 RNA polymerase. Expression of N, the viral polymerase protein (L), and a minireplicon containing a reporter gene was sufficient to reconstitute functional virus nucleocapsids. Coexpression of NSs, however, led to a dose-dependent decrease in reporter activity without affecting expression of controls. The inhibition could not be reversed by overexpression of N, L or the minireplicon, indicating that the NSs effect was not caused by a reduction in virus gene expression. The NSs proteins of two other members of the Bunyavirus genus, Guaroa virus and Lumbo virus, were also inhibitory in our system. The intracellular localisation of Bunyamwera virus NSs was investigated and found to be predominantly cytoplasmic, but intranuclear inclusion was also detected. Taken together, these data suggest that, in mammalian cells, the bunyavirus NSs protein controls the activity of the viral polymerase by a highly conserved mechanism.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Blotting, Western
  • Bunyamwera virus / drug effects
  • Bunyamwera virus / enzymology
  • Bunyamwera virus / genetics*
  • Bunyamwera virus / physiology*
  • Cell Line
  • Cell Nucleus / metabolism
  • Cell Nucleus / virology
  • Cricetinae
  • Cytoplasm / metabolism
  • Cytoplasm / virology
  • DNA-Directed RNA Polymerases / genetics
  • DNA-Directed RNA Polymerases / metabolism
  • Dose-Response Relationship, Drug
  • Fluorescent Antibody Technique
  • Genes, Reporter / genetics
  • Molecular Sequence Data
  • Nucleocapsid / biosynthesis
  • Nucleocapsid / genetics
  • Protein Transport
  • RNA, Viral / biosynthesis*
  • RNA, Viral / genetics
  • Replicon / drug effects
  • Replicon / genetics*
  • Sequence Alignment
  • Viral Nonstructural Proteins / chemistry
  • Viral Nonstructural Proteins / genetics
  • Viral Nonstructural Proteins / metabolism*
  • Viral Nonstructural Proteins / pharmacology
  • Viral Proteins
  • Virus Replication* / drug effects


  • RNA, Viral
  • Viral Nonstructural Proteins
  • Viral Proteins
  • bacteriophage T7 RNA polymerase
  • DNA-Directed RNA Polymerases