40xUAS sequences followed by an Hsp70 basal promoter are fused upstream of sequence encoding Mmus\Cd8a - 'dfr288' - T2A - GFP. 'dfr288' is a fragment that extends from -99 to +189bp relative to the first annotated stop codon of vvl; it contains a 3' mRNA stem loop and promotes stop codon readthrough in cell culture reporter assays. In the absence of stop codon readthrough, only Mmus\Cd8a is expressed from the construct. In the presence of stop codon readthrough, both Mmus\Cd8a and GFP are expressed (the T2A peptide ensures they are translated as separate proteins).