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.
Narayanan
K
K
Department of Microbiology and Immunology, The University of Texas Medical Branch at Galveston, Galveston, Texas 77555-1019, USA.
Maeda
A
A
Maeda
J
J
Makino
S
S
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