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Journal of Virology, September 2000, p. 8127-8134, Vol. 74, No. 17
Department of Microbiology and Immunology,
The University of Texas Medical Branch at Galveston, Galveston,
Texas 77555-1019, and Department of Microbiology and Institute for
Cellular and Molecular Biology, The University of Texas at Austin,
Austin, Texas 78712-1095
Received 30 March 2000/Accepted 8 June 2000
Coronavirus contains three envelope proteins, M, E and S, and a
nucleocapsid, which consists of genomic RNA and N protein, within the
viral envelope. We studied the macromolecular interactions involved in
coronavirus assembly in cells infected with a murine coronavirus, mouse
hepatitis virus (MHV). Coimmunoprecipitation analyses demonstrated an
interaction between N protein and M protein in infected cells.
Pulse-labeling experiments showed that newly synthesized,
unglycosylated M protein interacted with N protein in a pre-Golgi
compartment, which is part of the MHV budding site. Coimmunoprecipitation analyses further revealed that M protein interacted with only genomic-length MHV mRNA, mRNA 1, while N protein
interacted with all MHV mRNAs. These data indicated that M protein
interacted with the nucleocapsid, consisting of N protein and mRNA 1, in infected cells. The M protein-nucleocapsid interaction occurred in
the absence of S and E proteins. Intracellular M protein-N protein
interaction was maintained after removal of viral RNAs by RNase
treatment. However, the M protein-N protein interaction did not occur
in cells coexpressing M protein and N protein alone. These data
indicated that while the M protein-N protein interaction, which is
independent of viral RNA, occurred in the M protein-nucleocapsid complex, some MHV function(s) was necessary for the initiation of M
protein-nucleocapsid interaction. The M protein-nucleocapsid interaction, which occurred near or at the MHV budding site, most probably represented the process of specific packaging of the MHV
genome into MHV particles.
0022-538X/00/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
Characterization of the Coronavirus M Protein and
Nucleocapsid Interaction in Infected Cells
*
Corresponding author. Mailing address: Department of
Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, TX 77555-1019. Phone: (409) 772-2323. Fax: (409)
772-5065. E-mail: shmakino{at}utmb.edu.
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