Summary of the site directed mutagenesis of uAUG codons. (Top) The Kozak consensus sequence favorable for ribosomal initiation.29 The most critical residues, positions −3 and +4, are typed in bold characters. Left column: sequence context of TPO uAUG codons. Residues in positions −3 and +4 that match the Kozak consensus are typed in boldface. Right column: mutations in uAUG sequences designed to inactivate ribosomal initiation.