Sequence requirements for efficient translational frameshifting in the Escherichia coli dnaX gene and the role of an unstable interaction between tRNA(Lys) and an AAG lysine codon.
Synthesis of the gamma-subunit of DNA polymerase III holoenzyme depends on precise and efficient translational frameshifting to the -1 frame at a specific site in the dnaX gene of Escherichia coli. In vitro mutagenesis of this frameshift site demonstrated the importance of an A AAA AAG heptanucleotide sequence, which allows two adjacent tRNAs to retain a stable interaction with mRNA after they slip to the -1 position. The AAG lysine codon present in the 3' half of this heptanucleotide was a key element for highly efficient frameshifting. A tRNA(Lys) with a CUU anticodon, which has a strong affinity for AAG lysine codons, is present in eukaryotic cells but absent in E. coli. Expression in E. coli of a mutant tRNA(Lys) with a CUU anticodon specifically inhibited the frameshifting at the AAG codon, suggesting that the absence of this tRNA in E. coli contributes to the efficiency of the dnaX frameshift.
Tsuchihashi
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Howard Hughes Medical Institute, Stanford University Medical Center, California 94305.
Brown
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D001483:Base Sequence; D003062:Codon; D004926:Escherichia coli / Q000235:genetics*; D016368:Frameshift Mutation; D015870:Gene Expression; D005798:Genes, Bacterial; D005814:Genes, Viral; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D010957:Plasmids; D014176:Protein Biosynthesis; D012333:RNA, Messenger / Q000235:genetics; D012357:RNA, Transfer, Lys / Q000235:genetics* / Q000378:metabolism; D013604:T-Phages / Q000235:genetics
D003062:Codon; D012333:RNA, Messenger; D012357:RNA, Transfer, Lys