The RNA Helicase Ded1 Interacts with Cell Cycle Components and Other Key Proteins During Cellular Stress

Abstract

DEAD-box RNA helicases regulate each stage of the RNA life-cycle during gene expression. Ded1 is an essential yeast DEAD-box protein that regulates translation initiation through its effects on mRNA secondary structure and formation of pre-initiation complexes. Ded1 binding to mRNA is not sequence specific, and therefore, it relies on interaction partners for its specificity and regulatory activities during initiation. Stress conditions require large-scale changes in translation that upregulate certain stress response genes but repress most other nonstress-related genes. The target-of-rapamycin (TOR) pathway is a major regulator of these changes, and we have found that Ded1 is a critical mediator of this stress response. Interestingly, in contrast to its role in promoting translation initiation in pro-growth conditions, Ded1 plays an active role in repressing translation upon TOR inactivation. My work focuses on further characterizing the currently unknown interactions critical for Ded1’s repressive function during cellular stress. My results support a physical interaction between Ded1 and Cdc28 in stress conditions that is absent in normal growth conditions, and follow-up results suggest that this interaction may help to coordinate the cell cycle and translation during stress. Along with this clear connection to Cdc28, I conducted a large-scale screen that also shows connections of Ded1 with ATP transport, stress granule formation, cellular localization, cellular trafficking, and mitochondrial translation. All of these could play a key role in understanding how Ded1 fits into the larger picture of translational regulation during TOR inactivation and each subset seen in the annotated GO terms could be an individual area of study for future understanding of stress responses and translation.