UBP43, an ISG15-specific deconjugating enzyme: expression, purification, and enzymatic assays.

UBP43 is the only deconjugating enzyme for the protein ISGylation system thus far identified. UBP43 activity is not critical for precursor processing, as UBP43-deficent cells can generate ISG15 conjugates upon type I interferon treatment. However, UBP43 deficiency caused a defect in the negative regulation of type I interferon signaling, resulting in enhanced and prolonged activation of Jak/Stat upon type I interferon treatment. This chapter describes the expression, purification, and enzymatic assays for UBP43.