Translational dysregulation in cancer: eIF4A isoforms and sequence determinants of eIF4A dependence.

The malignant phenotype is largely the consequence of dysregulated gene expression. Transformed cells depend upon not just a global increase in protein synthesis but an altered translational landscape in which pro-oncogenic mRNAs are translationally up-regulated. Such mRNAs have been shown to possess longer and more structured 5'-UTRs requiring high levels of eukaryotic initiation factor 4A (eIF4A) helicase activity for efficient translation. As such there is a developing focus on targeting eIF4A as a cancer therapy. In order for such treatments to be successful, we must develop a detailed understanding of the mechanisms which make specific mRNAs more dependent on eIF4A activity than others. It is also crucial to fully characterize the potentially distinct roles of eIF4A1 and eIF4A2, which until recently were thought to be functionally interchangeable. This review will highlight the recent advances made in this field that address these issues.