Characterization of the coronavirus M protein and nucleocapsid interaction in infected cells.
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.
Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-1019, USA.
K
K
Narayanan
A
A
Maeda
J
J
Maeda
S
S
Makino
D000818:Animals; D002460:Cell Line; D018352:Coronavirus Infections / Q000378:metabolism*; D000086862:Coronavirus M Proteins; D000086462:Coronavirus Nucleocapsid Proteins; D004591:Electrophoresis, Polyacrylamide Gel; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D006517:Murine hepatitis virus / Q000378:metabolism*; D019251:Nucleocapsid / Q000378:metabolism*; D019590:Nucleocapsid Proteins; D011233:Precipitin Tests; D011485:Protein Binding; D012333:RNA, Messenger / Q000378:metabolism; D012367:RNA, Viral / Q000032:analysis; D012259:Ribonuclease, Pancreatic / Q000378:metabolism; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins / Q000378:metabolism; D014763:Viral Matrix Proteins / Q000378:metabolism*; D019065:Virus Assembly / Q000502:physiology
D000086862:Coronavirus M Proteins; D000086462:Coronavirus Nucleocapsid Proteins; D008562:Membrane Glycoproteins; D019590:Nucleocapsid Proteins; D012333:RNA, Messenger; D012367:RNA, Viral; D064370:Spike Glycoprotein, Coronavirus; D014759:Viral Envelope Proteins; D014763:Viral Matrix Proteins; D012259:Ribonuclease, Pancreatic