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Journal of Virology, February 2001, p. 1459-1475, Vol. 75, No. 3
Departments of Microbiology and
Immunology1 and
Pediatrics3 and Elizabeth B. Lamb Center for Pediatric Research,2 Vanderbilt
University School of Medicine, Nashville, Tennessee 37232, and
Department of Medical Microbiology and Infectious Diseases,
University of Manitoba, Winnipeg, Manitoba,4 and
Department of Biochemistry, Microbiology and Immunology,
Faculty of Medicine, University of Ottawa, Ottawa,
Ontario,5 Canada
Received 12 June 2000/Accepted 26 October 2000
Progeny virions of mammalian reoviruses are assembled in the
cytoplasm of infected cells at discrete sites termed viral inclusions. Studies of temperature-sensitive (ts) mutant viruses
indicate that nonstructural protein
0022-538X/01/$04.00+0 DOI: 10.1128/JVI.75.3.1459-1475.2001
Copyright © 2001, American Society for Microbiology. All rights reserved.
Reovirus
NS Protein Is Required for Nucleation
of Viral Assembly Complexes and Formation of Viral Inclusions
NS and core protein µ2 are
required for synthesis of double-stranded (ds) RNA, a process that
occurs at sites of viral assembly. We used confocal immunofluorescence microscopy and ts mutant reoviruses to define the roles of
NS and µ2 in viral inclusion formation. In cells infected with
wild-type (wt) reovirus,
NS and µ2 colocalize to large,
perinuclear structures that correspond to viral inclusions. In cells
infected at a nonpermissive temperature with
NS-mutant virus
tsE320,
NS is distributed diffusely in the cytoplasm and
µ2 is contained in small, punctate foci that do not resemble viral
inclusions. In cells infected at a nonpermissive temperature with
µ2-mutant virus tsH11.2, µ2 is distributed diffusely in
the cytoplasm and the nucleus. However,
NS localizes to discrete structures in the cytoplasm that contain other viral proteins and are
morphologically indistinguishable from viral inclusions seen in cells
infected with wt reovirus. Examination of cells infected with wt
reovirus over a time course demonstrates that
NS precedes µ2 in
localization to viral inclusions. These findings suggest that viral
RNA-protein complexes containing
NS nucleate sites of viral
replication to which other viral proteins, including µ2, are
recruited to commence dsRNA synthesis.
*
Corresponding author. Mailing address: Lamb Center for
Pediatric Research, D7235 MCN, Vanderbilt University School of
Medicine, Nashville, TN 37232. Phone: (615) 343-9943. Fax: (615)
343-9723. E-mail:
terry.dermody{at}mcmail.vanderbilt.edu.
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