Identification of a second protein encoded by influenza C virus RNA segment 6

Hongō, Seiji; Sugawara, Kanetsu; Nishimura, Hidekazu; Muraki, Yasushi; Kitame, Fumio; Nakamura, Kenzo

doi:10.1099/0022-1317-75-12-3503

Cited by 42 publications

(65 citation statements)

References 29 publications

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“…Mouse monoclonal antibody (MAb) L2 against matrix protein M1 (31) has been described previously. Anti-glutathione S-transferase (GST)/CM2 rabbit serum was produced as described previously (9). Anti-GST/NS2, rabbit antiserum against the C-terminal region (residues 63 to 182) of C/NS2, and anti-GST/NS1, rabbit antiserum against the C-terminal region (residues 225 to 246) of C/NS1, were also produced as described previously (1).…”

Section: Methodsmentioning

confidence: 99%

“…RNA segment 6 (M gene) of C/Yamagata/1/88 is 1,181 nucleotides in length and has a single open reading frame (positions 27 to 1148) capable of encoding a polypeptide of 374 amino acids with a predicted M r of 42,000 (9,35). However, the predominant mRNA transcript of this RNA segment lacks nucleotides 755 to 982 and encodes a 242-amino-acid matrix (M1) protein with an M r of 27,000.…”

mentioning

confidence: 99%

“…However, the predominant mRNA transcript of this RNA segment lacks nucleotides 755 to 982 and encodes a 242-amino-acid matrix (M1) protein with an M r of 27,000. Elimination of the intron results in the introduction of a termination codon (consisting of nucleotides 753, 754, and 983) after amino acid residue 242 (9,35). Unspliced mRNA from RNA segment 6 is synthesized in infected cells, though at very low levels (13% of spliced mRNA) (9).…”

mentioning

confidence: 99%

“…Elimination of the intron results in the introduction of a termination codon (consisting of nucleotides 753, 754, and 983) after amino acid residue 242 (9,35). Unspliced mRNA from RNA segment 6 is synthesized in infected cells, though at very low levels (13% of spliced mRNA) (9). This mRNA species is capable of coding for a 374-amino-acid protein (P42) containing an additional 132 amino acids from the C terminus of M1 (11), which is cleaved by signal peptidase to generate CM2, composed of the C-terminal 115 amino acids, in addition to the M1Ј protein, composed of the N-terminal 259 amino acids (12,26).…”

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confidence: 99%

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Influenza C Virus NS1 Protein Upregulates the Splicing of Viral mRNAs

Muraki

Furukawa

Kohno

et al. 2010

J Virol

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The influenza C virus genome consists of seven singlestranded RNA segments of negative polarity. RNA segment 6 (M gene) of C/Yamagata/1/88 is 1,181 nucleotides in length and has a single open reading frame (positions 27 to 1148) capable of encoding a polypeptide of 374 amino acids with a predicted M r of 42,000 (9, 35). However, the predominant mRNA transcript of this RNA segment lacks nucleotides 755 to 982 and encodes a 242-amino-acid matrix (M1) protein with an M r of 27,000. Elimination of the intron results in the introduction of a termination codon (consisting of nucleotides 753, 754, and 983) after amino acid residue 242 (9, 35). Unspliced mRNA from RNA segment 6 is synthesized in infected cells, though at very low levels (13% of spliced mRNA) (9). This mRNA species is capable of coding for a 374-amino-acid protein (P42) containing an additional 132 amino acids from the C terminus of M1 (11), which is cleaved by signal peptidase to generate CM2, composed of the C-terminal 115 amino acids, in addition to the M1Ј protein, composed of the N-terminal 259 amino acids (12, 26). The CM2 protein forms a voltage-activated ion channel permeable to chloride ions (13). Recently, it has been suggested that CM2 also has pH-modulating activity (2).In influenza A virus-infected cells, the colinear transcript from segment 7 encodes M1, and the M1 mRNA also undergoes alternative splicing to generate spliced M2 mRNA and mRNA 3 . The colinear transcript and spliced mRNA from influenza A virus segment 8 are translated into NS1 and NS2 (NEP), respectively. It has been reported that the steady-state level of spliced viral transcripts is only 10% of that of unspliced viral transcripts in influenza A virus-infected cells (15,16). The inefficient splicing of viral pre-mRNAs can be understood partly by the fact that influenza A virus NS1 protein is associated with spliceosomes and inhibits pre-mRNA splicing (6,7,17). cis-acting sequences in the NS1 transcript also negatively regulates splicing (22). The splicing of influenza A virus M1 mRNA is controlled by the rate of nuclear export (34). The alternative splicing of influenza A virus M1 mRNA is regulated by the binding of the viral polymerase complex and cellular splicing factor SF2/ASF (28, 29). In the case of influenza C virus, however, the mechanism by which influenza C virus M mRNA is efficiently spliced has not yet been clarified. Influenza C virus RNA segment 7 (NS gene) encodes two nonstructural proteins, the 246-amino-acid NS1 protein (C/NS1), encoded by a colinear mRNA transcript of the gene, and the 182-amino-acid NS2 protein (C/NS2), encoded by a spliced mRNA (1,8,18) (see Fig. 5). Using transfected cells, Paragas et al. (25) have demonstrated that C/NS2 possesses nuclear export activity. We recently demonstrated that C/NS2 plays a role in the nuclear export of vRNP in influenza C virus-infected cells, and that C/NS2 is incorporated into virions, where it associates with

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Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Influenza C Virus NS1 Protein Upregulates the Splicing of Viral mRNAs

Muraki

Furukawa

Kohno

et al. 2010

J Virol

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“…The CM2 protein is abundantly expressed at the cell surface of virus-infected and cDNA-transfected cells and is incorporated into influenza C virions (17,36). The CM2 protein is encoded by influenza C virus RNA segment six (19). RNA segment six is initially transcribed into a colinear mRNA transcript, and a majority of this species is subsequently spliced to yield a second mRNA transcript (53).…”

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Identification of a Membrane Targeting and Degradation Signal in the p42 Protein of Influenza C Virus

Pekosz

Lamb

2000

J Virol

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Two mRNA species are derived from the influenza C virus RNA segment six, (i) a colinear transcript containing a 374-amino-acid residue open reading frame (referred to herein as the seg 6 ORF) which is translated to yield the p42 protein, and (ii) a spliced mRNA which encodes the influenza C virus matrix (CM1) protein consisting of the first 242 amino acids of p42. The p42 protein undergoes proteolytic cleavage at a consensus signal peptidase cleavage site after residue 259, yielding the p31 and CM2 proteins. Translocation of p42 into the endoplasmic reticulum membrane occurs cotranslationally and requires the hydrophobic internal signal peptide (residues 239 to 259), as well as the predicted transmembrane domain of CM2 (residues 285 to 308). The p31 protein was found to undergo rapid degradation after cleavage from p42. Addition of the 26S proteasome inhibitor lactacystin to influenza C virus-infected or seg 6 ORF cDNA-transfected cells drastically reduced p31 degradation. Transfer of the 17-residue C-terminal region of p31 to heterologous proteins resulted in their rapid turnover. The hydrophobic nature, but not the specific amino acid sequence of the 17-amino-acid C terminus of p31 appears to act as the signal for targeting the protein to membranes and for degradation.

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