eLife Assessment
In this important study, the authors employed state-of-the-art biochemistry, cryo-EM, and HDX mass spec approaches to study the formation of the binary Uba7-UBE2L6 and ternary UBA7-UBE2L6-ISG15 complexes. The results established mechanisms by which UBA7 and UBE2L6 form disulfide bonds, disrupting the ISG15 transfer cascade. While the biochemical and structural experiments are largely convincing, the mechanism under in vivo conditions remains unclear, due to the limited use of a single E2 enzyme. The authors need to repeat their experiments with a representative panel of human E2 enzymes.