Columbia College Science Scholars
My project focuses on examining regulation of translation at specific codons in E. coli. The genetic code is degenerate, and many theories exist to explain how that degeneracy is used to regulate gene expression. Current molecular biology textbooks maintain that increasing tRNA concentrations cognate to codons promotes more efficient translation at those codons, while lowering tRNA concentrations inhibits translation. Since tRNA concentration is proportional to the frequency of the cognate codons in an organism’s genome, common textbook dogma states that translational efficiency correlates with codon frequency. This past summer, I conducted streptomycin sensitivity assays, which monitor translational stress, to examine the effect of increasing tRNA concentrations cognate to rare codons. Contrary to expectations, we found that tRNA overexpression had very little effect on E. coli growth. In fact, for the AGG and AGA codons, the rarest codons in the E. coli genome, growth curves in overexpressed cells indicated that the cells were experiencing translational stress. I will be performing ribosome profiling experiments in the future to explain these results and to determine how cells exploit degeneracy in the genetic code to biochemically regulate gene expression.