Representative results of Ub-AMC assay depicting decreased activity of three exogenously expressed BAP1 missense mutant proteins (N78S, R383C, and S583L – corresponding to mutations seen in families ABS2570, ABS3023 and ABS3313, respectively) compared to the activity of the wild-type BAP1 protein. Exogenous expression of a BAP1 mutant construct corresponding to the S628fs*8 mutation (case ABS3428) showed no BAP1 activity. 293T cells were transfected with individual BAP1 expression constructs, and then protein levels for each construct were normalized prior to Ub-AMC assay. BAP1 and Ub-substrate were incubated for 15 min, and then fluorescence indicative of activity was assessed after 5, 10 and 15 min. A) Location of each BAP1 missense mutation and S628fs*8 mutation. B) Results of fluorescence activity observed in two representative Ub-AMC experiments to assay activity of exogenously expressed wild-type and mutant BAP1 proteins. The experiment was repeated a total of three times with similar results.