Quantifying the Roles of the Translation Initiation Factor eIF4H Isoforms and Their Relationship to Cancer Development

Regulation of protein synthesis plays a critical role in many cellular processes. Regulation is believed to mainly take place during translation initiation (TI), in which several TI factors (eIFs) associate to form a TI complex that facilitates ribosome assembly on the mRNA start codon. We aim to characterize and quantify the function of two isoforms of a small TI factor, eIF4H. Both isoforms stimulate the activity of eIF4A, the RNA helicase required for TI. Abnormality in eIF4H is linked to multiple diseases, such as predisposition to infections by Herpes simplex virus 1 (HSV-1), Williams-Beuren syndrome (WBS) and cancer. Previous studies suggest that the expression of both eIF4H isoforms is elevated as a result of NF-kB activation. This may indicate that eIF4HI over-expression stimulates pro-survival mechanism. Here we preform a quantitative mechanistic evaluation of the stimulatory effect of eIF4HI versus eIF4HII on eIF4A. To this end, we cloned, expressed and purified recombinant proteins and performed RNA unwinding assay using fluorescence reporters. Our hypothesis is that differences in RNA unwinding kinetics may shed light on the yet circumstantial connection of eIF4HI over-expression to tumorogenesis.