For CHIP-DNA2, lysates were clarified from sonicated nuclei and DNA2-DNA complexes were isolated with antibody. For collection of BrdU negative DNA, separation of BrdU-labeled DNA from unlabeled DNA was done as previously described (Roux-Michollet et al, 2010; Viggiani et al, 2010). Briefly, 20 µL of DNA at ~20 ng/µL in PBS was heat denatured at 100 ºC for 1 min, and transferred to an ice-ethanol bath for 30-50 s to flash freeze. Tubes of DNA were then thawed completely at RT (less than 3 min), mixed with 2 μL of a BrdU antibody (BD Biosciences, cat# 347580), and incubated at RT for 30-40 min in the dark with occasional mixing. The BrdU-labeled DNA, bound with antibody, was then isolated with 20 µL of prepared Dynabeads Sheep anti-Mouse IgG (Thermo Scientific cat# 11031). The BrdU-negative DNA was collected by sequencing. Libraries were constructed using Kapa's HyperPlus Kits