Recombinant NSMCE2 Has Auto-SUMOylation and SUMO-Chain Assembly Activities

Abstract

Homologous recombination (HR) is a high-fidelity repair mechanism that primarily functions during replication-associated DNA damage and plays a major role in preventing genomic instability. As an effective repair mechanism, HR is also postulated to drive tumor cell resistance to platinum-based chemotherapeutic agents that induce DNA damage. RAD51 is an essential protein in the HR pathway, and its overexpression has been associated with chemotherapy-resistant tumors. Thus, RAD51 and the SUMOylation processes involved in its regulation are of interest when looking for ways to combat this resistance. Depletion of the E3 SUMO ligase NSMCE2 inhibits RAD51 function in HR. Further, preliminary studies have identified a candidate compound, C3, that potentially inhibits NSMCE2 activity and increases cancer cell sensitivity to chemotherapy. Through recombinant protein expression in E. coli and affinity chromatography, I obtained partially purified polyhistidine-tagged NSMCE2 protein. This protein exhibits both auto-SUMOylation and SUMO-chain assembly activities in vitro. However, C3 inhibits neither of these activities. Altogether, this study provides insights into the function of NSMCE2 and sets up future studies to investigate the inhibition of NSMCE2 activity.