title: GSM5782059: MM468_GSKJ4_day91_H3K27me3; Homo sapiens; ChIP-Seq
library_construction_protocol: For MDA-MB-468 cell line, prior to scChIP-seq cells were  individualized and re-suspended in PBS/0.04% BSA (ThermoFisher Scientific, # AM2616).  For the PDX model, prior scChIP-seq and scRNA-seq, PDX were digested at 37°C for 2h with a cocktail of Collagenase I (Roche, # 11088793001) and Hyaluronidase (Sigma, # H3506) as previously described (Petit et al, Lab Investigation 2013). Cells were further individualized at 37°C using a cocktail of 0.25% trypsin/Versen (ThermoFisher Scientific, #15040-033), Dispase II (Sigma, # D4693) and Dnase I (Roche, # 11284932001). Red Blood Cell lysis buffer (ThermoFisher Scientific, # 00-4333-57) was then added to degrade red blood cells. To increase the viability of the cell suspension, we removed dead cells using a Dead Cell Removal kit (Miltenyi Biotec). Cells were re-suspended in PBS/0.04% BSA (ThermoFisher Scientific, # AM2616).  After immunoprecipitation targeting H3K4me3 or H3K27me3, scChIP-seq libraries were prepared as following: barcoded-nucleosomes were amplified by in vitro transcription using the T7 MegaScript kit (ThermoFisher Scientific). The resulting amplified RNA was purified using 1x RNAClean XP beads (Beckman) and reverse transcribed by random priming in cDNA. After RNA digestion, DNA was amplified by PCR using with Illumina Primers for 12 cycles and library fragments ranging from 300 to 600 bp (single-cell barcode plus nucleosomal sequence + PCR primer sequence) were size-selected on an agarose gel. Single-cell ChIP-seq libraries were sequenced on Illumina NextSeq 500 MidOutput 150 cycles After immunoprecipitation targeting H3K27me3, scChIP-seq libraries were prepared as following: barcoded-nucleosomes were amplified by in vitro transcription using the T7 MegaScript kit (ThermoFisher Scientific). The resulting amplified RNA was purified using 1x RNAClean XP beads (Beckman) and reverse transcribed by random priming in cDNA. After RNA digestion, DNA was amplified by PCR using with Illumina Primers for 12 cycles and library fragments ranging from 300 to 600 bp (single-cell barcode plus nucleosomal sequence + PCR primer sequence) were size-selected on an agarose gel. Single-cell ChIP-seq libraries were sequenced on Illumina NextSeq 500 MidOutput 150 cycles