1. Mohiuddin_Figure S1 10 min 2 h A B 10 min 2 h 5 h

2. Mohiuddin_Figure S2 MfeI BamHI MARCO TR pTOPO Digest with BamHI & MfeI Digest with BglII & EcoRI BglII EcoRI IRES GFP pMSCV AID BglII EcoRI IRES GFP pMSCV MARCO TR BamHI MfeI BglII EcoRI IRESGFP pMSCV MARCO TR B Human cells (293T cells) Genetically modified Retroviral expression vector Helper plasmid (pCLampho) Viral supernatant WT, △ FEN1 & △ REV3 DT40 cells WT cells with chimera, △ FEN1 cells with chimera & △ REV3 cells with chimera C A TR BamHI AvrII P1 P2 MARCO AvrII MfeI P3 P5 TOPO Cloning TR BamHI AvrII MARCO BamHI MfeI TOPO Cloning AvrII BamHI Digest with BamHI & AvrII MARCO BamHI MfeI AvrII TR BamHI AvrII Ligate AvrII pTOPO MfeI BamHI MARCO TR pTOPO Digest with AvrII TR MARCO C C T A G G G G A T C C SI Nuclease TR MARCO C G G C Ligate BamHI MARCO TR pTOPO MfeI AvrII P4

3. Mohiuddin_Figure S3

4. Mohiuddin_Figure S4 WT WT + Beads Green Fluorescence Red Fluorescence Forward Scatter Side Scatter Count 24 h after exposure WT with Long Chimera WT with Long Chimera + Beads WT with Short Chimera WT with Short Chimera + Beads Green Fluorescence Red Fluorescence Forward Scatter Side Scatter Count 24 h after exposure A

5. Mohiuddin_Figure S4 (continued) B WT WT + Beads Green Fluorescence Red Fluorescence Forward Scatter Side Scatter Count 3 h after exposure WT with Long Chimera WT with Long Chimera + Beads WT with Short Chimera WT with Short Chimera + Beads Green Fluorescence Red Fluorescence Forward Scatter Side Scatter Count 3 h after exposure WT WT with Short Chimera WT with Long Chimera Without Beads With Beads C

6. Table S1: List of primers used to make chimeric receptor. Name Sequence P1 (+) ATTAGGATCCATGGATCATGCCAGAGCAGCATTGTCTAAC P2 ( -) ATTACCTAGGAAGATGACAGGCGGTCCTTGAATCTC P3 (+) ATTACCTAGGGACACAAAGGAGAACGCGGTCC P4 (+) ATTACCTAGGTGGAAATCTTTCACCAAGGGTCCTGG P5 (- ) ATTACAATTGTCAGACACACTCCACGCCGGCGTC