Figure 1.

Positioning of ribosomes on a messenger RNA. The 5' cap is to the left and the poly(A) tail is to the right. The red symbols depict non-random accumulation of ribosomes at an uORF, the initiation codon, a site of ribosome pausing within the coding sequence (CDS), and at termination. The green symbols represent freely translating ribosomes at random sites along the coding sequence.