Messenger RNA encoding the phosphoprotein (P) gene of human parainfluenza virus 3 is bicistronic.

The complete nucleotide sequence of the phosphoprotein (P) mRNA of human parainfluenza virus 3 (PIV-3) was derived from two cDNA clones spanning almost the entire P gene. The mRNA, excluding the poly(A) tail, is 2014 nucleotides long and is bicistronic. The first open reading frame (ORF) codes for the phosphoprotein (P) of mol wt 68,860. Seven nucleotides downstream from the first AUG codon, in a +1 reading frame, there is an additional ORF which can code for a polypeptide of mol wt 23,266. The latter protein appears to be similar to the C proteins found in cells infected with several paramyxoviruses. Comparison of the predicted amino acid sequence of the P and C proteins of PIV-3 with the corresponding Sendai virus proteins reveals considerable homology at the C-terminal half. In contrast, the P and C proteins of PIV-3 share very little homology with the measles virus P and C proteins, respectively.