Transient expression and sequence of the matrix (M1) gene of WSN influenza A virus in a vaccinia vector

A cDNA encoding the entire amino acid sequence of the matrix (M1) protein of influenza A/WSN/33 virus was cloned, sequenced, and expressed in a vaccinia virus system consisting of the T7 bacteriophage RNA polymerase and a plasmid carrying the M1 gene flanked by T7 polymerase promoter and terminator sequences. The transiently expressed M1 gene product comigrated on SDS-polyacrylamide gels with the endogenous WSN virus M1 protein and was recognized in Western blot analysis by three epitope-specific monoclonal antibodies directed to the M1 protein. The nucleotide sequence and the predicted amino acid sequence of the cloned WSN virus M1 coding region was found to be more than 97% homologous to that of the M1 gene of influenza virus A/PR/8/34 reported by G. Winter and S. Fields (Nucleic Acids Res. 8, 1965-1974, 1980).