Accuracy and Efficiency of Protein Synthesis Elongation in Escherichia coli

The translation process can be perturbed during the elongation phase. "Recoding" events utilize signals embedded in certain messenger RNAs which reprogram ribosomes to shift reading frames or read through stop codons, among other unexpected behaviors. The efficiency of the translation process is also subject to variability depending on levels of uncharged tRNAs, as well as the codon composition, structure, and stability of mRNAs. Codon utilization among synonym codons varies widely from organism to organism, and between highly expressed and poorly expressed genes in the same organism. This laboratory has focused on effects of uncharged tRNA, translational frameshifts and other recoding events, and effects of codon bias in Escherichia coli. In earlier work, we showed in vivo that uncharged tRNA can affect translation by entering the ribosomal "A" site, with implica?tions for how the "stringent response" occurs. With respect to translational frameshifts, we have provided strong evidence for a model in which +1 (rightward) translational frameshifts are governed by the speed of the ribosome and the extent of vacancy of the A site. With respect to codon bias, we have developed a vector system for assessing the influence of rare codons on translation, and have shown that both consecu?tive rare arginine and rare leucine codons significantly inhibit expression at the translational level. We have reported an unexplained new finding, termed "5' translational blockage," in which consecutive low-usage codons show much greater inhibition of translation when they are located near the translation start site compared to the middle of the gene.

Selected Publications

• Shu P, Dai H, Mandecki W and Goldman E., 2004, CCC CGA is a weak translational recoding site in Escherichia coli. Gene, in press.
  
  
• Song L, Mandecki, W and Goldman, E., 2003, Expression of non-open reading frames isolated from phage display due to translation reinitiation. FASEB J. 17:1674-1681.
  
  
• Zemsky J, Mandecki W and Goldman, E., 2002, Genetic analysis of the basis of translation in the -1 frame of an unusual non ORF sequence isolated from phage display. Gene Expression 10:109-114.
  
  
• Cheng, L. and Goldman, E., 2001, Absence of effect of varying Thr-Leu codon pairs on protein synthesis in a T7 system. Biochem. 40:6102-6106.
  
  
• Goldman, E., Korus, M. and Mandecki, W., 2000, Efficiencies of translation in three reading frames of unusual non-ORF sequences isolated from phage display. FASEB J. 14:603-611.