Interaction of NDRG1 and TGM2 Modulates DNA Replication and Repair

In tumor cells, DNA replication is constantly challenged by endogenous and exogenous sources, referred to as replication stress, and various pathways have evolved to mitigate this stress in cancer. We recently identified a novel extracellular matrix-induced DNA repair pathway involving NDRG1 (N-myc downstream regulated gene 1). Matrix-induced signaling results in NDRG1-dependent protection from chemotherapy-induced replication stress. To uncover further mechanistic details of NDRG1-mediated effects on DNA replication, we identified Transglutaminase 2 (TGM2) as a novel NDRG1 binding partner. TGM2 is an acyltransferase that catalyzes Ca(2+)-dependent protein modifications. This interaction was enriched upon chemotherapy-induced replication stress and also upon ECM-induced signaling. Our data show that TGM2 depletion significantly slows replication fork progression, and this phenotype is dependent on TGM2 catalytic activity and its nuclear localization. Our study further identified a putative NDRG1-TGM2 binding site and show that the physical interaction between NDRG1 and TGM2 is required for efficient DNA replication. Implications: This study reveals a previously unrecognized nuclear function for NDRG1 and TGM2 in regulating DNA replication fork stability and recovery and uncovers a stress-responsive mechanism that supports replication homeostasis in cancer cells and advance our understanding of how extracellular signals are integrated with replication and repair pathways.