Initiation of translation at CUG, GUG, and ACG codons in mammalian cells

Gene. 1990 Jul 16;91(2):173-8. doi: 10.1016/0378-1119(90)90085-6.


Site-directed mutants of the ACG start codon of the C' protein encoded in the polycistronic Sendai virus P/C mRNA revealed that CUG, GUG, and ACG codons initiated translation rather efficiently (10-30% of the AUG initiation) in COS-1 host cells. In addition, AUA and AUU codons initiated translation at about 5% efficiency, while UUG did not initiate translation. The sequence context of these start codons (purine residues at -3 and +4) was crucial in their recognition by the ribosome. The location of the non-AUG codons in the P/C mRNA did not play a role in its recognition by ribosomes. By using CUG, the most efficient non-AUG start codon, instead of the original ACG codon and inserting an additional upstream CUG codon in the P/C mRNA, the amount of the C' protein was increased and a novel protein was synthesized. Syntheses of an increased level of C' and the novel protein did not affect downstream initiations of the P and C proteins, suggesting that more ribosomes bind the mRNA than are actually utilized for initiation of translation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Base Sequence
  • Cell Line
  • Codon*
  • Mutagenesis, Site-Directed
  • Parainfluenza Virus 1, Human / genetics*
  • Precipitin Tests
  • Protein Biosynthesis*
  • RNA, Viral / genetics
  • Ribosomes / metabolism


  • Codon
  • RNA, Viral