Identification of an amino acid residue on influenza C virus M1 protein responsible for formation of the cord-like structures of the virus.
Influenza C virus-like particles (VLPs) have been generated from cloned cDNAs. A cDNA of the green fluorescent protein (GFP) gene in antisense orientation was flanked by the 5' and 3' non-coding regions of RNA segment 5 of the influenza C virus. The cDNA cassette was inserted between an RNA polymerase I promoter and terminator of the Pol I vector. This plasmid DNA was transfected into 293T cells together with plasmids encoding virus proteins of C/Ann Arbor/1/50 or C/Yamagata/1/88. Transfer of the supernatants of the transfected 293T cells to HMV-II cells resulted in GFP expression in the HMV-II cells. The quantification of the GFP-positive HMV-II cells indicated the presence of approximately 10(6) VLPs (ml supernatant)(-1). Cords 50-300 microm in length were observed on transfected 293T cells, although the cords were not observed when the plasmid for M1 protein of C/Ann Arbor/1/50 was replaced with that of C/Taylor/1233/47. A series of transfection experiments with plasmids encoding M1 mutants of C/Ann Arbor/1/50 or C/Taylor/1233/47 showed that an amino acid at residue 24 of the M1 protein is responsible for cord formation. This finding provides direct evidence for a previous hypothesis that M1 protein is involved in the formation of cord-like structures protruding from the C/Yamagata/1/88-infected cells. Evidence was obtained by electron microscopy that transfected cells bearing cords produced filamentous VLPs, suggesting the potential role of the M1 protein in determining the filamentous/spherical morphology of influenza C virus.
Muraki
Yasushi
Y
Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
Washioka
Hiroshi
H
Department of Anatomy and Cell Biology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
Sugawara
Kanetsu
K
Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
Matsuzaki
Yoko
Y
Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
Takashita
Emi
E
Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
Hongo
Seiji
S
Department of Bacteriology, Yamagata University School of Medicine, Iida-Nishi, Yamagata 990-9585, Japan.
D000595:Amino Acid Sequence; D002460:Cell Line; D017930:Genes, Reporter; D006801:Humans; D009982:Gammainfluenzavirus / Q000737:chemistry / Q000648:ultrastructure*; D007668:Kidney; D008854:Microscopy, Electron; D008969:Molecular Sequence Data; D010957:Plasmids / Q000235:genetics; D014162:Transfection; D014763:Viral Matrix Proteins / Q000737:chemistry*
C031540:M-protein, influenza virus; C488936:M1 protein, Influenza A virus; D014763:Viral Matrix Proteins