Identification and nucleotide sequence of the gene encoding a surface antigen induced by vaccinia virus

The gene encoding the specific antigen (S antigen) induced on the surface of vaccinia virus-infected cells was mapped on the viral genome by the construction of recombinant viruses. The S gene is located in the 1.5-kbp XbaI-AccII fragment between 11.1 and 12.6 kbp from the right end of the viral genome. Nucleotide sequencing of the fragment revealed an open reading frame (ORF) of 351 codons capable of producing a polypeptide with a molecular weight (MW) of 40,701 Da. Mapping of the S mRNA by primer extension indicates the presence of the transcription initiation site that precedes the translation initiation codon by 14 nucleotides. The region preceding the S mRNA start site is extremely A/T-rich and has sequence similarity with other early genes. The signal for termination of transcription of the early genes, TTTTTAT, is included near the end of the ORF. The deduced amino acid sequence contains a typical membrane signal characterized by a hydrophobic region in the N-terminus. An early polypeptide with a MW of 40 kDa, in agreement with the size predicted from the ORF, was synthesized by cell-free translation of the mRNA selected by hybridization to a plasmid containing the region of the ORF.