Monoclonal antibody analysis of influenza virus matrix protein epitopes involved in transcription inhibition.

Influenza virus M1 protein has been shown to inhibit viral RNA transcription, and in this study the epitopes on M1 critical for this function were localized. When a battery of 15 monoclonal anti-M1 antibodies were reacted with chemically cleaved fragments of M1 on a western blot, five distinct banding patterns were observed. A representative antibody was selected from each banding group, and its ability to reverse M1-effected transcription inhibition was measured. From these data, the sites on M1 critical for transcription inhibition were deduced. It appears now that the regions on M1 in the vicinity of amino acid residues #70 and #140 are critical for inhibition. Furthermore, by taking into account the hydropathicity and secondary structure, it is hypothesized that amino acids #70 and #140 are physically close together in the final three-dimensional conformation of M1 protein and that the residues in between form a loop and are thus removed from the functional site.