Regulation of MAGE‐A3/6 by the CRL4‐DCAF12 ubiquitin ligase and nutrient availability. (24th May 2019) - Ravichandran, Ramya
Abstract: Melanoma antigen genes (MAGEs) are emerging as important oncogenic drivers that are normally restricted to expression in male germ cells but are aberrantly expressed in cancers and promote tumorigenesis. Mechanistically, MAGEs function as substrate specifying subunits of E3 ubiquitin ligases. Thus, the activation of germline‐specific genes in cancer can drive metabolic and signaling pathways through altered ubiquitination to promote tumorigenesis. However, the mechanisms regulating MAGE expression and activity are unclear. Here, we describe how the MAGE‐A3/6 proteins that function as repressors of autophagy are downregulated in response to nutrient deprivation. Short‐term cellular starvation promotes rapid MAGE‐A3/6 degradation in a proteasome‐dependent manner. Proteomic analysis reveals that degradation of MAGE‐A3/6 is controlled by the CRL4‐DCAF12 E3 ubiquitin ligase. Importantly, the degradation of MAGE‐A3/6 by CRL4‐DCAF12 is required for starvation‐induced autophagy. These findings suggest that oncogenic MAGEs can be dynamically controlled in response to stress to allow cellular adaptation, autophagy regulation, and tumor growth and that CRL4‐DCAF12 activity is responsive to nutrient status. Synopsis: The CRL4‐DCAF12 E3 ubiquitin ligase controls MAGE‐A3/6 protein abundance to tune autophagy in response to cellular starvation. The cancer‐specific MAGE‐A3/6 proteins are rapidly ubiquitinated and degraded by the proteasome upon nutrient deprivation. The CRL4‐DCAF12 E3 ubiquitin ligase controls MAGE‐A3/6 protein stability through recognition of a C‐terminal degron. Degradation of MAGE‐A3/6 by CRL4‐DCAF12 is important for autophagy induction upon nutrient deprivation. Abstract : The CRL4‐DCAF12 E3 ubiquitin ligase controls MAGE‐A3/6 protein abundance to tune autophagy in response to cellular starvation.