B03: Stress-dependent regulation of organellar proteome plasticity by dynamic selection of different translation initiation sites

Proteomic plasticity, i.e. changing the quality and quantity of cellular and organellar proteomes, is essential for the adaptation of cellular function to external and internal cues. An efficient and rapid way to redirect proteins is translation from the same mRNA but using different initiation sites that alter organellar targeting information. Changes in the cellular levels of different redox species, in particular H2O2, constitute an important cue that has been linked to differentiation, proliferation, hypoxia signaling, senescence and cell cycle progression. Unbalanced levels of these redox species may covalently modify DNA, RNA and proteins, and thereby simultaneously compromise the fidelity of mRNA and protein biosynthesis. Cellular generation of H2O2 is highly compartmentalized and necessitates organelle-specific responses. We aim to mechanistically understand dynamic selection of different translation initiation sites upon H2O2 signaling as a rapid and efficient way to achieve changes in organellar proteomes in human cells. To this end, we will profile the usage of alternative translation initiation sites under unperturbed and H2O2 challenged conditions using ribosome sequencing experiments. We will thereby test whether bolus H2O2 treatments and localized H2O2 generation result in different responses. In parallel, we will employ proteomic experiments to assess the dynamic changes in organellar proteomes. Further, we will investigate the mechanisms translating H2O2 signals to changes in initiation site selection. Lastly, we will assess how the fidelity of this process becomes perturbed during preexisting chronic oxidative stress, a hallmark of many human pathologies. Collectively, we will connect the translation initiation landscape with organellar proteome information to understand organellar proteome plasticity during redox signaling and how fidelity loss affects this plasticity.