Regulated degradation of Chk1 by chaperone-mediated autophagy in response to DNA damage

Chaperone-mediated autophagy(definition) (CMA) is activated in response to cellular stressors to prevent cellular proteotoxicity through selective degradation of altered proteins in lysosomes. Reduced CMA activity contributes to the decrease in proteome quality in disease and ageing. Here, we report that CMA is also upregulated in response to genotoxic insults and that declined CMA functionality leads to reduced cell survival and genomic instability. This role of CMA in genome quality control is exerted through regulated degradation of activated checkpoint kinase 1 (Chk1) by this pathway after the genotoxic insult. Nuclear accumulation of Chk1 in CMA-deficient cells compromises cell cycle progression and prolongs the time that DNA damage persists in these cells. Furthermore, blockage of CMA leads to hyperphosphorylation and destabilization of the MRN (Mre11–Rad50–Nbs1) complex, which participates in early steps of particular DNA repair pathways. We propose that CMA contributes to maintain genome stability by assuring nuclear proteostasis(definition). Chaperone-mediated autophagy (CMA) helps maintain protein quality during cellular stress. Here the authors show that CMA is also activated in response to DNA damage and regulates degradation of the cell cycle regulator Chk1—the first nuclear protein shown to be a substrate of CMA.