Stem cell function and sensitivity to genotoxic stress is controlled by protein translation rates

Whether protein synthesis and cellular stress response pathways interact to control stem cell functions is currently unknown. Here, we show that skin stem cells synthesise less protein than their immediate progenitors in vivo, even when forced to proliferate in a tumour model. Our analyses reveal that activation of stress response pathways drives both a global reduction of protein synthesis and altered translation of specific mRNAs that together promote stem cell functions and tumourigenesis. Mechanistically we show that inhibition of post-transcriptional cytosine-5 methylation locks stem cells in this distinct translational inhibition programme. Paradoxically, this stress-induced translation inhibition renders stem cells hypersensitive to genotoxic stress, as tumour regeneration after treatment with 5-fluorouracil is blocked. Thus, stem cells must revoke translation inhibition pathways to regenerate a tissue or tumour.