GCN4 translational control. The positions of the uORFs (open boxes) in the 5' leader sequence are drawn roughly to scale. The main GCN4 ORF is depicted partially. Point mutations that remove the start codon of a uORFs are labelled by cross. (A) Wild type GCN4 mRNA structure. (B) Cartoon of GCN4 mRNA translation. (C-E) GCN4-lacZ constructs that were used to investigate GCN4 translation under repressing and derepressing conditions, the activities of which are denoted as A 1, A 2 and A 3, respectively.