SEQUENCE OF THE PHOSPHOPROTEIN GENE OF PNEUMONIA VIRUS OF MICE - EXPRESSION OF MULTIPLE PROTEINS FROM 2 OVERLAPPING READING FRAMES

The gene encoding the phosphoprotein of the pneumovirus pneumonia viru s of mice (PVM) has been cloned and sequenced. The gene is 903 nucleot ides in length and contains a long open reading frame (ORF) capable of encoding a polypeptide of 295 amino acid residues. A smaller, second, overlapping ORF encoding a polypeptide 137 amino acids in length was also present. The large ORF directed the synthesis of a 39-kDa polypep tide and four additional polypeptides with masses of 37 kDa, 26 kDa, 2 3 kDa, and 16 kDa in vitro. The smaller polypeptides were-generated by internal initiation on in-frame AUG initiation codons to generate car boxy co-terminal products. Western immunoblot analysis indicated that at least two of these proteins and several other related polypeptides are present in infected cells, and the possible origins of these are d iscussed. Western blot analysis using antiserum raised against a synth etic peptide and specific for the predicted second ORF product identif ied a polypeptide of 23 kDa in PVM-infected cells. The pattern of PVM P gene expression is unlike that of the closely related respiratory sy ncytial virus and is reminiscent of that of paramyxoviruses such as Se ndai virus. This is the first example of a pneumovirus encoding multip le polypeptide products from a single mRNA in vivo.