Bn 34

For western blots, cells were treated with 0.3 mM HU for 4 hr, harvested and directly lysed in Laemmli buffer (Bio-Rad), boiled for 5 min and loaded on SDS-PAGE gels.
Antibodies used for immunoblots in SIRF, PLA and iPOND are as follows: MLL3 (Abcam 1:100), MRE11 (Abcam 12D7 1:200), RAD52 (Santa Cruz F7 1:50), POL θ (Abcam 1:100), RAD51 (Abcam 14B4 1:200), mouse biotin (Sigma-Aldrich BN-34 1:100), rabbit biotin (Cell Signaling D5A7 1:200), p53 (Santa Cruz DO1, 1:1000), ORC2 (Abcam, SB46, 1:1000) and PCNA (Santa Cruz, PC10, 1:1000).

Antibodies used in SIRF and PLA assays are as follows: mouse anti-biotin (Sigma-Aldrich, BN-34), rabbit anti-biotin (Cell Signaling Technology, D5A7), rabbit anti-XRCC3 (Abnova, PAB24835), mouse anti-RAD51C (Abnova, H00005889-M01), rabbit anti-RAD51C (Abcam, ab72063), and mouse anti-RAD51 (Abcam, ab213). Antibodies used in immunoblotting and immunoprecipitation are mouse anti-RAD51C (Novus, NB100-177) and rabbit anti-XRCC3 (Novus, NB100-165). Antibodies used in DNA fiber assays are anti-IDU (BrdU, Beckton Dickinson, 347580, 1:50) and CldU (BrdU, Abcam, ab6326, 1:100). More detailed antibody information can be found in the Supplementary Table 3. Uncropped and unprocessed scans of Western blots and gels can be found in the Source data file.