All flow cytometry was performed using LSRFortessa Flow Cytometer (BD Biosciences). GFP linked shRNA competition assays were performed as described previously(80 (link)). Apoptosis was assayed using APC-Annexin V (Tonbo biosciences) or Annexin V-FITC Kit (Miltenyi Biotec). All data were processed and analyzed with FCS Express 7 Research Edition (De Novo Software, Inc; RRID:SCR_016431). All data plotted with GraphPad (Prism, RRID:SCR_002798).