biostudies-literatureWise HMIntramural NIH HHSMedical Research CouncilWellcome TrustBiotechnology and Biological Sciences Research Councile1002998https://www.ebi.ac.uk/biostudies/studies/S-EPMC3486900biostudies-literatureUnknown8(11)Segment 7 of influenza A virus produces up to four mRNAs. Unspliced transcripts encode M1, spliced mRNA2 encodes the M2 ion channel, while protein products from spliced mRNAs 3 and 4 have not previously been identified. The M2 protein plays important roles in virus entry and assembly, and is a target for antiviral drugs and vaccination. Surprisingly, M2 is not essential for virus replication in a laboratory setting, although its loss attenuates the virus. To better understand how IAV might replicate without M2, we studied the reversion mechanism of an M2-null virus. Serial passage of a virus lacking the mRNA2 splice donor site identified a single nucleotide pseudoreverting mutation, which restored growth in cell culture and virulence in mice by upregulating mRNA4 synthesis rather than by rPLoS pathogensIdentification of a novel splice variant form of the influenza A virus M2 ion channel with an antigenically distinct ectodomain.PMC3486900088789BBS/E/D/20241864075450G0700815G0700848G0801931Stuart ADHutchinson ECKang ZHWise HMDigard PFodor ETaubenberger JKJagger BWKash JCSchwartzman LMFirth AEGog JRRobb NfalseIdentification of a novel splice variant form of the influenza A virus M2 ion channel with an antigenically distinct ectodomain.Segment 7 of influenza A virus produces up to four mRNAs. Unspliced transcripts encode M1, spliced mRNA2 encodes the M2 ion channel, while protein products from spliced mRNAs 3 and 4 have not previously been identified. The M2 protein plays important roles in virus entry and assembly, and is a target for antiviral drugs and vaccination. Surprisingly, M2 is not essential for virus replication in a laboratory setting, although its loss attenuates the virus. To better understand how IAV might replicate without M2, we studied the reversion mechanism of an M2-null virus. Serial passage of a virus lacking the mRNA2 splice donor site identified a single nucleotide pseudoreverting mutation, which restored growth in cell culture and virulence in mice by upregulating mRNA4 synthesis rather than by r2012-01-01T00:00:00Z20122025-07-09T03:05:08.388Z2025-07-09T03:05:08.388ZS-EPMC34869002313338610.1371/journal.ppat.1002998