NSMCE1 is a component of the SMC5-SMC6 complex, a complex involved in DNA double-strand breaks by homologous recombination. The complex may promote sister chromatid homologous recombination by recruiting the SMC1-SMC3 cohesin complex to double-strand breaks. The complex is required for telomere maintenance via recombination in ALT (alternative lengthening of telomeres) cell lines and mediates sumoylation of shelterin complex (telosome) components which is proposed to lead to shelterin complex disassembly in ALT-associated PML bodies (APBs). NSMCE1 has in vitro ubiquitin ligase activity in presence of NDNL2. Recombinant human NSMCE1 protein, fused to His-tag at N-terminus, was expressed in E.coli and purified by using conventional chromatography techniques.