Alternative transcription start site selection leads to large differences in translation activity in yeast

Alternative 5′ UTR isoforms differ in capacity for cap-independent translation. (A) Representative ethidium bromide stained gels used to normalize luciferase activity to mRNA concentrations. (B) Mean normalized luciferase activity from translation of uncapped (5′-GTP) mRNAs. Error bars represent standard deviations. P-values were calculated by Student's t-test (two-tailed); (*) P < 0.05; (**) P < 0.01; (***) P < 0.001. (C) Comparison of mean translation activity to 5′ UTR length and (D) predicted stability as determined by free-energy minimization using mfold (Zuker 2003).