Research Projects

Eukaryotic initiation factor 2 (eIF2) is a crucial factor in protein synthesis, delivering methionyl-initiator tRNA (Met-tRNAi) to the ribosomal preinitiation complex to recognize the start codon (AUG) in mRNA. However, during cellular stress, the alpha subunit of eIF2 gets phosphorylated, inactivating the eIF2 complex and shutting down translation. Unlike eIF2, which has three subunits, eIF2A delivers tRNA in a codon-dependent manner. This differs from eIF2, which has only one polypeptide chain and uses GTP hydrolysis for its activity. EIF2A plays a critical role in the synthesis of polypeptides in mammals, including antigen presentation, integrated stress response, and tumor initiation. Knockout leads to decreased lifespan and metabolic disorders. In mammals, eIF2A mediates the translation of hepatitis C viral (HCV) mRNA and proto-oncogene c-Src mRNA under stress conditions. To understand the mechanism of eIF2A-mediated polypeptide synthesis, it is essential to determine the structures of eIF2A-bound ribosomal complexes. Preliminary results show that recombinant yeast eIF2A independently binds Met-tRNAi and small ribosomal subunit (40S). A low-resolution map of yeast eIF2A-bound 40S ribosomal subunit was obtained using cryo-electron microscopy, but model building was not possible due to the low resolution. The project proposes using both yeast and mammalian systems to capture eIF2A with tRNA and mRNA on the 40S. Mutational and biochemical investigations will be conducted to validate the interactions of eIF2A with tRNA and 40S.