RGG motif-containing Scd6/LSM14A proteins regulate the translation of specific mRNAs in response to hydroxyurea-induced genotoxic stress

RGG motif-containing proteins are the second largest group of RNA-binding proteins. Here, we identify a unique and conserved role of yeast Scd6 and its human ortholog LSM14A in hydroxyurea (HU)-mediated genotoxic stress response. Scd6/LSM14A, but not all tested RGG-containing proteins, localize to cytoplasmic puncta in an RGG-dependent manner upon HU treatment. The absence of Scd6 increases cellular HU tolerance under normal conditions but sensitizes the cells to HU upon overexpression of SRS2, which is known to dampen the response to DNA damage. Scd6 binds the SRS2 mRNA to repress its translation upon HU stress. This interaction occurs in cytoplasmic granules and is modulated by the arginine methylation status of Scd6 and the Scd6 LSm domain, which acts as a cis-regulator of Scd6 arginine methylation. Polysome profiling experiments indicate that LSM14A regulate the translation of mRNAs encoding non-homologous end joining (NHEJ) DNA damage repair factors such as DNL4 (DNA ligase 4) and RTEL1 (the Srs2 ortholog), as well as the NHEJ activity in response to HU. Overall, the work shows the contribution of arginine methylation and the RGG-containing proteins Scd6/LSM14A in the genotoxic stress response by determining the translation status of a subset of mRNAs. We performed transcriptome and translatome analysis (RNA-Seq) on A2058 melanoma cells transfected with scrambled siRNA or siRNA specific to LSM14A cells and treated with hydroxyurea (HU) or not (NT).