Two mRNAs that differ by two nontemplated nucleotides encode the amino coterminal proteins P and V of the paramyxovirus SV5

The “P≓ gene of the paramyxovirus SV5 encodes two known proteins, P (M(r) ≈ 44,000) and V (M(r) ≈ 24,000). The complete nucleotide sequence of the “P≓ gene has been obtained and is found to contain two open reading frames, neither of which is large enough to encode the P protein. We have shown that the P and V proteins are translated from two mRNAs that differ by the presence of two nontemplated G residues in the P mRNA. These two additional nucleotides convert the two open reading frames to one of 392 amino acids. The P and V proteins are amino coterminal and have 164 amino acids in common. The unique C terminus of V consists of a cysteine-rich region that resembles a cysteine-rich metal binding domain. An open reading frame that contains this cysteine-rich region exists in all other paramyxovirus “P≓ gene sequences examined, which suggests that it may have important biological significance.