Structural insights into translation initiation on canonical and non-canonical start codons

• Applicant: Professor Dr. Daniel Nicodemus Wilson
• Subject Area: Structural Biology ; Biochemistry
• Term: since 2026
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 574433608

Translation initiation, the first step in protein synthesis, is a highly regulated and complex process. It is considered to be the most divergent and complex step among the different kingdoms of life. Translation initiation involves the assembly of initiation factors, mRNA and initiator tRNA, with the ribosomal subunits to form functional initiation complexes. This phase is pivotal, as it is the rate limiting step, and selects the correct reading frame for the mRNA, thus serving as a major checkpoint. In bacteria, such as E. coli, the majority of highly expressed mRNAs bind to the 30S ribosomal subunit via the Shine-Dalgarno (SD) sequence, ensuring proper alignment of the start codon, typically the canonical AUG, with the initiator tRNA's anticodon. Bacterial translation initiation also occurs on non-canonical start codons, such as GUG, UUG, CUG and AUU, which are employed to modulate the efficiency of translation initiation and thereby regulate the synthesis of specific proteins. Despite decades of biochemical and structural research, the absence of high-resolution structures of 30S translation initiation complexes has limited our understanding of this fundamentally important process. Here we aim to determine high resolution cryo-electron microscopy structures of bacterial 30S and 70S initiation complexes to provide much needed structural insight into the role of the initiation factors IF1, IF2 and IF3 during translation initiation. Moreover, we will compare structures on mRNAs containing canonical AUG start codons and non-canonical start codons to compare and contrast these diverging processes. Insights into how the context of the start codon influences the efficiency of translation initiation will be unravelled by determining structures of initiation complexes formed on mRNAs with varying nucleotide context upstream and downstream of the start codon. We will also structurally analyse initiation complexes formed on the physiological infC mRNA, which encodes the translation initiation factor IF3, to provide mechanistic insight into the autoregulatory system that operates through monitoring the levels of cellular IF3 and thereby modulating the efficiency of translation initiation. Collectively, our study will generate a molecular movie of translation initiation at unprecedented resolution, providing molecular insight into this fundamental process.

• DFG Programme: Research Grants