Production of the C-terminal WD domain of WDR91 (residues 392-747) containing an N-terminal His6-tag and used for adinity-based DEL selection was described previously . DEL selection was performed using a KingFisher Duo Prime Purification System (ThermoFisher) in a 96-well plate. 250 pmol of WDR91 was captured by 35 µL of Ni-charged MagBeads (Genscript L00295) in selection buder (20 mM HEPES, 0.01% Triton-X(w/v), 5 mM MgCl2, 150 mM NaCl, 0.3 mg/mL salmon sperm DNA, 10 mM imidazole, pH 7.5) for 30 min. The immobilized protein was incubated with the DEL decks for 1 hour at room temperature, followed by five 1-min washes in 500 μL of selection buder at room temperature. The retained DEL compounds were recovered by heat elution in the elution buder (20 mM HEPES, 300 mM NaCl, pH 7.5) at 95 °C for 15 min. After the first round of selection, a second round was performed using the heat-eluted sample of the previous round as the input and 250 pmol of fresh bead-immobilized WDR91. Empty Ni-charged MagBeads were used as the negative control to subtract the beads' background. After each step, the heat-eluted output was quantified by quantitative PCR. After three rounds of DEL selection, the heat-eluted output was prepared for DNA sequencing and data analysis.