Project Summary Our research program focuses on the mechanism of eukaryotic protein synthesis and translational control. The two projects we are currently studying are: (1) the mechanism of translational control by the fragile X mental retardation protein (FMRP), and (2) the mechanism of translation initiation on influenza A virus (IAV) mRNAs. Fragile X syndrome is a disease that afflicts about 100,000 Americans and about 3 million people worldwide, resulting in intellectual disability, childhood seizures, and autistic behavior in the patients. The disease is caused by the transcriptional silencing of the fragile X mental retardation 1 gene (FMR1). FMR1 gene codes for an RNA-binding protein, FMRP, which is highly expressed in the brain and is essential for the normal development of the brain. Mammals have two autosomal paralogs of FMRP designated as fragile X related 1 and 2 (FXR1 and FXR2) proteins. FMRP, FXR1 and FXR2 have been implicated in regulating the translation of several mRNAs. However, the precise mechanism by which these proteins regulate the expression of these mRNAs is unknown. The goal of the first project is to understand the molecular mechanism underlying the regulation of protein synthesis by FMRP, FXR1 and FXR2. We will use a robust in vitro translation system, biochemical techniques and quantitative biophysical methods to significantly advance our understanding of the molecular mechanism used by FMRP, FXR1 and FXR2 to regulate protein synthesis. Results of these studies will provide useful insights in identifying potential drug targets to treat fragile X syndrome. The goal of the second project is to investigate the mechanism of translation initiation by IAV mRNAs. IAV is responsible for several thousand deaths annually and is a severe threat to global public health. We have new data that indicate that IAV mRNAs may use a non-canonical mechanism of translation initiation. Our studies show that poly A binding protein 1 (PABP1) binds to the highly conserved sequences present in the 5’-UTR of IAV mRNAs. Additionally, we show that the translation of the IAV mRNA is more resistant to the inactivation of eukaryotic initiation factor 4E (eIF4E) compared to a control mRNA. We hypothesize that the recruitment of PABP1 to the viral 5’-UTRs tethers eIF4G and promote the assembly of the translation initiation complex in an eIF4E-independent manner. This may favor the translation of IAV mRNAs under cellular stress conditions in the cell, which is known to reduce the activity of eIF4E. We will determine whether the binding of PABP1 to the 5’- UTR of IAV mRNAs is essential for translation initiation and the viral cycle using in vitro techniques and cellular IAV infection studies. Our research will lead to fundamental new knowledge about the process of translation initiation on IAV mRNAs, which could help in the development of new antiviral drugs.