title: GSM4726990: U2OS_siCtrl_H4K20me1_t16_ChIP-seq; Homo sapiens; ChIP-Seq
library_construction_protocol: Cells were formaldehyde fixed and lysed in ice-Cold IP buffer and sonicated to an average length of 300 to 1000 bp fragments using Bioruptor bath-based sonicator. After checking for fragment size 500 µg of chromatin lysate was pre-cleared with 40 µl of Protein-A sepharose beads (BSA blocked) for 1 h and incubated overnight at 4ºC on rotation with 5 µg of primary ChIP-grade antibody. Blocked Protein-A sepharose beads were then added next day to the chromatin and  incubated at 4ºC on rotation for 3-4 h. Samples were subsequently washed and DNA was decrosslinked overnight and purified using Qiagen PCR purification columns. Chipped DNA was quantified using Qubit dsDNA HS kit. Libraries were prepared from 5 ng of Chipped DNA using NEBNext Ultra II library preparation kit according to manusfacturer's protocol.