Mediator MED23 induces premature senescence by interacting with BCLAF1 via blocking autophagy flux in lung cancer cells

macroautophagy/autophagy plays a key role in regulating the balance between cell survival and senescence during the progression of lung cancer. Med23 (also known as Sur2), a protein belonging to an evolutionarily conserved high-molecularmass complex composed of more than 20 distinct subunits, promotes the growth, metastasis , and migration of lung cancer cells and is overexpressed in multiple cancers. However, the function of MED23 in autophagy regulation remains unknown. Here, we observes that MED23 expression is significantly upregulated in a subset of cancer cells and reversely correlated with overall survival rates and clinical stage for lung cancer patients. Mechanistically, MED23 is found to interact with BCLAF1 (BCL-2-associated transcription factor 1, BTF) ,a nuclear protein that can induce apoptosis and autophagy. Moreover, BCLAF1 interacts with the promoter of NUPR1 and downregulates its expression. We further show that BCLAF1 and MED23 depletion inhibits autophagy and induces premature senescence in vitro. Remarkably, the expression of BCLAF1 and MED23 are negatively correlated with NUPR1 in the human lung cancer tissues and adjacent normal tissues. Collectively, our data reveal a physical and genetic interaction between BCLAF1 and MED23, suggesting that MED23 constitutes a molecular node in the regulatory network of autophagy and this pathway may be an important therapeutic target in lung cancer.