A SMALL HIGHLY BASIC-PROTEIN IS ENCODED IN OVERLAPPING FRAME WITHIN THE P-GENE OF VESICULAR STOMATITIS-VIRUS

Vesicular stomatitis virus (VSV) has served for several decades as the prototype rhabdovirus and a model RNA virus. Extensive studies upheld the original view of VSV genetics with simply five genes (N, P, M, G, and L), each encoding a single unique protein. We now report the firs t unambiguous demonstration of the existence of an additional unique p rotein encoded in an overlapping frame within the virus P gene. Experi ments using antipeptide sera specific for the predicted second open re ading frame have demonstrated the synthesis of two N-terminally nested forms of the protein in virus-infected cells. The major form is 55 am ino acids in length, whereas the minor form has 10 additional N-termin al amino acids. Ribosome initiation of synthesis of these proteins app ears to occur at AUG codons, 68 and 41 bases, respectively, downstream of the P protein AUG initiation codon. The proteins are found in the cytoplasm of the infected cell but are undetectable in purified virion s, consistent with their being nonstructural proteins. Both the major and minor forms of the protein are highly basic and arginine rich, rem iniscent of the C and C' proteins encoded in overlapping frame close t o the 5' terminus of the P mRNA of several paramyxoviruses. The potent ial to encode small, highly basic proteins within the P mRNA 5' termin us is highly conserved among the vesiculoviruses.