@article{mbs:/content/journal/jgv/10.1099/vir.0.79937-0, author = "Muraki, Yasushi and Washioka, Hiroshi and Sugawara, Kanetsu and Matsuzaki, Yoko and Takashita, Emi and Hongo, Seiji", title = "Identification of an amino acid residue on influenza C virus M1 protein responsible for formation of the cord-like structures of the virus", journal= "Journal of General Virology", year = "2004", volume = "85", number = "7", pages = "1885-1893", doi = "https://doi.org/10.1099/vir.0.79937-0", url = "https://www.microbiologyresearch.org/content/journal/jgv/10.1099/vir.0.79937-0", publisher = "Microbiology Society", issn = "1465-2099", type = "Journal Article", abstract = "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 106 VLPs (ml supernatant)−1. Cords 50−300 μm 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.", }