Marilyn Kozak analyzed 5'-noncoding sequences from 699 vertebrate mRNAs to identify patterns in translation initiation. The consensus sequence for vertebrate translation initiation is (GCC)GCCATGG, with the most conserved position being a purine at -3 (upstream of the ATG codon), present in 97% of vertebrate mRNAs. G repeats at positions -3, -6, and -9 are notable. Only 10% of vertebrate mRNAs have upstream ATG codons, except for oncogene transcripts, where two-thirds have ATG codons before the major open reading frame. Most vertebrate mRNA leader sequences range from 20 to 100 nucleotides. Shorter and longer sequences have different significance. The study confirms previous findings about the non-random nature of sequences around the initiator codon. The GCC motif in positions -9 to -7 remains to be fully understood. The most efficient initiators are those with A at -3 and G at +4. Only six mRNAs lack the preferred nucleotides in these positions. The study also discusses the role of upstream ATG codons, which are rare but significant in oncogenes. The context around the initiator codon is crucial for translation initiation. The study highlights the importance of leader length and the potential impact of secondary structure on translation efficiency. It also notes errors in cDNA sequences that may not represent the functional mRNA. The findings suggest that the 5'-noncoding sequences play a critical role in translation initiation and regulation in vertebrates.Marilyn Kozak analyzed 5'-noncoding sequences from 699 vertebrate mRNAs to identify patterns in translation initiation. The consensus sequence for vertebrate translation initiation is (GCC)GCCATGG, with the most conserved position being a purine at -3 (upstream of the ATG codon), present in 97% of vertebrate mRNAs. G repeats at positions -3, -6, and -9 are notable. Only 10% of vertebrate mRNAs have upstream ATG codons, except for oncogene transcripts, where two-thirds have ATG codons before the major open reading frame. Most vertebrate mRNA leader sequences range from 20 to 100 nucleotides. Shorter and longer sequences have different significance. The study confirms previous findings about the non-random nature of sequences around the initiator codon. The GCC motif in positions -9 to -7 remains to be fully understood. The most efficient initiators are those with A at -3 and G at +4. Only six mRNAs lack the preferred nucleotides in these positions. The study also discusses the role of upstream ATG codons, which are rare but significant in oncogenes. The context around the initiator codon is crucial for translation initiation. The study highlights the importance of leader length and the potential impact of secondary structure on translation efficiency. It also notes errors in cDNA sequences that may not represent the functional mRNA. The findings suggest that the 5'-noncoding sequences play a critical role in translation initiation and regulation in vertebrates.