title: GSM7111128: MCF10A, 10uM Nutlin3a, Replicate 1; Homo sapiens; OTHER
library_construction_protocol: As previously described in (Levandowski, C. B.; Jones, T.; Gruca, M.; Ramamoorthy, S.; Dowell, R. D.; Taatjes, D. J, 2021), after treatment the cells were washed 3x with ice cold PBS, and then treated with 10 ml (per 15 cm plate) ice-cold lysis buffer (10 mM Tris–HCl pH 7.4, 2 mM MgCl2, 3 mM CaCl2, 0.5% NP-40, 10% glycerol, 1 mM DTT, 1x Protease Inhibitors (1mM Benzamidine (Sigma B6506-100G), 1mM Sodium Metabisulfite (Sigma 255556-100G), 0.25mM Phenylmethylsulfonyl Fluoride (American Bioanalytical AB01620), and 4U/mL SUPERase-In). Cells were centrifuged with a fixed-angle rotor at 1000xg for 15 min at 4◦C. Supernatant was removed and pellet was resuspended in 1.5 mL lysis buffer to a homogenous mixture by pipetting 20-30X before adding another 8.5 mL lysis buffer. Suspension was centrifuged with a fixed-angle rotor at 1000xg for 15 min at 4◦C. Supernatant was removed and pellet was resuspended in 1 mL of lysis buffer and transferred to a 1.7 mL pre-lubricated tube (Costar cat. No. 3207). Suspensions were then pelleted in a microcentrifuge at 1000xg for 5 min at 4◦C. Next, supernatant was removed and pellets were resuspended in 500 μL of freezing buffer (50 mM Tris pH 8.3, 40% glycerol, 5 mM MgCl2, 0.1 mM EDTA, 4U/ml SUPERase-In). Nuclei were centrifuged 2000xg for 2 min at 4◦C. Pellets were resuspended in 100 μL freezing buffer. To determine concentration, nuclei were counted from 1 μL of suspension and freezing buffer was added to generate 100 μL aliquots of 10x106 nuclei. Aliquots were flash frozen in liquid nitrogen and stored at −80◦C. Nuclear run-on experiments were performed as described previously (Mahat, D. B., Kwak, H., Booth, G. T., Jonkers, I. H., Danko, C. G., Patel, R. K., et al. (2016). Base-pair-resolution genome-wide mapping of active RNA polymerases using precision nuclear run-on (PRO-seq). Nature Protocols, 11(8), 1455–1476. with the following modifications: the final concentration of non-biotinylated CTP was raised from 0.25 μM to 25 μM, a clean-up and size selection was performed using 1X AMPure XP beads (1:1 ratio) (Beckman) prior to test PCR and final PCR amplification, and the final library clean-up and size selection was accomplished using 1X AMPure XP beads (1:1 ratio) (Beckman).