RGG-motif protein Scd6 affects oxidative stress response by regulating cytosolic caTalase T1 (Ctt1)

In response to stress, cells undergo gene expression reprogramming to cope with external stimuli. Cells utilize a conserved stress response mechanism called global downregulation of translation, leading to the storage of translationally repressed mRNAs in RNA granules. During oxidative stress induced by H2O2, genes responsible for combating oxidative stress, such as catalases, are strongly induced. However, the post-transcriptional regulatory events affecting these genes during H2O2 stress are not well-explored. Scd6, an RGG-motif-containing protein in yeast, acts as a translational repressor through its interaction with eIF4G1. This study identifies the role of Scd6 in oxidative stress response by regulating cytoplasmic catalase T1 (CTT1). We observe that peroxide stress induces the assembly of Scd6 puncta, which do not colocalize with P-bodies or stress granules. Scd6 overexpression increased sensitivity, while deletion enhanced tolerance to H2O2 treatment. Increased ROS accumulation and decreased Ctt1 protein levels were observed upon Scd6 overexpression due to translation repression of CTT1 mRNA. CTT1 mRNA interacts with Scd6. smFISH analysis and RNA immunoprecipitation studies reveal that localization of Scd6 to puncta upon peroxide stress reduces its interaction with CTT1 mRNA, allowing derepression. The role of Scd6 in peroxide stress response is conserved since the human homolog LSm14A also localizes to puncta upon H2O2 stress, and its overexpression reduces survival in response to peroxide stress. Overall, this study identifies a unique example of translation regulation whereby stress-induced localization of the translation repressor protein to puncta leads to derepression of the target mRNA.