RNA granules and DNA damage: Exploring the role of posttranscriptional gene control upon genotoxic stress

Abstract

Cells constantly encounter genotoxic stress arising from extrinsic environmental factors or intrinsic metabolic byproducts. In response, cells activate a robust DNA damage response (DDR) network to preserve genomic stability. Whether stressors that affect the nucleus can stimulate posttranscriptional response in the cytoplasm remains poorly explored. While DDR pathways have been extensively studied at the transcriptional and post-translational levels, the regulation of specific mRNA translation during genotoxic stress remains less understood. In this work, we explore the role of specific RNA-binding proteins (RBPs) in modulating mRNA translation under genotoxic stress conditions, using Saccharomyces cerevisiae as a model system. This work uncovers a critical, yet underappreciated, layer of gene expression control that operates rapidly and reversibly in the cytoplasm. The first part of my work uncovers the role of a highly conserved, RGG-motif containing protein Scd6 in regulating the translation of a DNA helicase SRS2 upon hydroxyurea induced genotoxic stress. We identify SRS2 as a translation repression target of Scd6 and this repression activity is independent of eIF4G1 binding. We also observe that this repression is modulated by arginine methylation and requires localization of Scd6 and SRS2 mRNA to cytoplasmic mRNA-protein condensates called processing bodies (P-bodies). In the second part of our study, we investigate the function of another, related, RGG-motif containing RBP, Sbp1, under similar genotoxic stress conditions. Here, we uncover a previously unknown role for Sbp1 in regulating autophagy, a conserved catabolic process that supports cell survival during stress. Our findings reveal that Sbp1 localizes to P-bodies in an RGG dependent manner and represses translation of key autophagy-related mRNAs, ATG1, ATG2 and ATG9 under hydroxyurea treatment. Deletion of SBP1 leads to enhanced autophagic flux and improved stress tolerance. These findings suggest that Sbp1 acts as a translation checkpoint, preventing premature or excessive activation of autophagy during stress response. Together, these studies provide new insights into how RBPs coordinate the translational landscape during genotoxic stress by repressing specific mRNAs through their localization to RNA-protein condensates such as P-bodies. This mode of regulation is rapid, reversible, and conserved. It underscores the importance of cytoplasmic post-transcriptional control in determining cell fate during genotoxic stress. Importantly, these findings open avenues for investigating similar mechanisms in mammalian systems. The conservation of Scd6-like proteins (for e.g., LSM14A in humans) and the increasing recognition of stress granules and P-bodies in diseases such as cancer and neurodegeneration highlight the translational potential of this work. Understanding these mechanisms could improve therapeutic strategies targeting translation regulation in diseases characterized by genome instability and stress sensitivity, including cancer.