Location of possible alternative start codons within the IE-3 gene. a) Spliced nucleotide sequence of IE-3 exons 2, 3 and the first part of exon 5 showing in frame start codons (bold) and those identified as having an elevated probability of being actual start codons (underlined) when analyzed with an algorithm designed to identify possible start codons in raw sequence data. b) Sequence of 5' untranslated region and putative start codon (bold) of the exon 5-164 transcript. The underlined region is the Kozak sequence. c) Western blot of protein lysates prepared from M2-10B4 cells 48 hours following transfection with pcDNA 3.1 expression plasmids containing either exons 2, 3 and 5 or exon 5 alone, using anti-IE-3 antibody. An anti-V5 antibody was also used to confirm the banding pattern observed with the IE-3 antibody was specific for the transfected exon 2-5 plasmid (right panel).