Structure of the host-derived sequences present at the 5′ ends of influenza virus mRNA

Nucleotide sequence analysis of the terminal virus-coded regions of a clone of the matrix gene of influenza virus indicated that the region corresponding to the 5' end of the mRNA contains an additional 13 non-virus coded nucleotides. Using the dideoxy-chain termination sequencing method with a restriction fragment derived from this clone, we have determined that the 5' ends of matrix gene mRNAs contain a heterogenous sequence of 9-15 nucleotides. In addition, the data indicate that the 3' terminal nucleotide of matrix gene virion RNA is not transcribed into mRNA, transcription of influenza virus-specific sequences commencing with the penultimate nucleotide at the 3' end of viron RNA.