Abstract
ATM serine/threonine kinase (ATM; previously known as ataxia-telangiectasia mutated) plays a critical role in maintaining genomic stability and regulates multiple downstream pathways, such as DNA repair, cell cycle arrest, and apoptosis. As a serine/threonine kinase, ATM has an array of downstream phosphorylation substrates, including checkpoint effector checkpoint kinase 2 (CHK2). ATM inhibits cell cycle progression by phosphorylating and activating CHK2, which plays an important role in the formation and development of tumors and participates in DNA repair responses after double-stranded DNA breaks. In this study, we used a recently developed mammalian functional genetic screening system to explore a series of ATM substrates and their role in DNA damage to enhance our understanding of the DNA damage response. Ubiquilin 4 (UBQLN4), which belongs to the ubiquilin family characterized by its ubiquitin-like (UBL) and ubiquitin-associated (UBA) domains, was identified as a new substrate for ATM. UBQLN4 is involved in various intracellular processes, such as autophagosome maturation, p21 regulation, and motor axon morphogenesis. However, the biological function of UBQLN4 remains to be elucidated. In this study, we not only identified UBQLN4 as a substrate for ATM, but also found that UBQLN4 interacts with and stabilizes the anti-apoptotic proteins Bcl-2-related protein A1 (BCL2A1) and Bcl-2-like protein 10 (BCL2L10) and prevents mesothelioma cell apoptosis in response to DNA damage. These findings expand our understanding of the role of UBQLN4 in mesothelioma and provide new insights into potential mesothelioma treatments targeting substrates for ATM.