Absence of effect of varying Thr-Leu codon pairs on protein synthesis in a T7 system.
The over-represented threonine-leucine (Thr-Leu) codon pair ACG CUG has been previously reported to be inhibitory to translation compared to the synonymous under-represented Thr-Leu codon pair ACC CUG, in an E. coli system in which the codon pairs were located either 3 and 4, or 6 and 7, or 9 and 10 codons downstream from the initiating codon for the message [Irwin, B., Heck, J. D., and Hatfield, G. W. (1995) J. Biol. Chem. 270, 22801-22806]. In the work reported here, these synonymous codon pairs were tested in a T7 system, with the codon pairs located either 14 and 15, or 6 and 7 codons downstream from the AUG start codon. In contrast to the reported findings in the E. coli system, there was no difference found in translation between mRNAs containing the respective codon pairs in the T7 system. The reasons for the different findings remain unclear, but presumably are a consequence of differences between the E. coli and T7 systems used to assay gene expression. Nevertheless, as a result of this work, it appears that the effect of varying codon pairs reported in the E. coli system is not due to a difference in translational step times through the respective codon pairs, as previously proposed.
Cheng
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Graduate School of Biomedical Sciences, New Jersey Medical School, Department of Microbiology & Molecular Genetics, University of Medicine and Dentistry of New Jersey, 185 South Orange Avenue, Newark, New Jersey 07103, USA.
Goldman
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D017123:Bacteriophage T7 / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D003001:Cloning, Molecular / Q000379:methods; D003062:Codon / Q000138:chemical synthesis / Q000235:genetics / Q000378:metabolism*; D012321:DNA-Directed RNA Polymerases / Q000235:genetics / Q000378:metabolism; D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics; D015967:Gene Expression Regulation, Viral; D005822:Genetic Vectors / Q000138:chemical synthesis; D007930:Leucine / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D016254:Mutagenesis, Insertional; D010957:Plasmids / Q000138:chemical synthesis; D014176:Protein Biosynthesis; D013912:Threonine / Q000235:genetics* / Q000378:metabolism; D014764:Viral Proteins / Q000096:biosynthesis* / Q000235:genetics*; D001616:beta-Galactosidase / Q000235:genetics
D003062:Codon; D014764:Viral Proteins; D013912:Threonine; C062210:bacteriophage T7 RNA polymerase; D012321:DNA-Directed RNA Polymerases; D001616:beta-Galactosidase; D007930:Leucine