F) Comparing activity of USP1WT and USP1PIP1 (+UAF1) on PCNA-UbWT and PCNA-UbPIM1 in gel-based assays shows that the activity of USP1WT is severely reduced by the PIM1 mutation in PCNA, whereas USP1PIP1 activity is not further affected indicating that PIP1 and PIM mutation affect the same interaction (n=2, technical replicates (example shown here from 1 of 2 biological replicates)). 