title: GSM4878940: K562 e7i rep1; Homo sapiens; OTHER
library_construction_protocol: Fix 1 million cells with 1% Formaldehyde in culture medium at room temperature for 10 minutes. Wash the cells with PBS. Resuspend with reaction buffer (50mM Tris acetate, pH 7.5, 150mM potassium acetate, 10mM magnesium acetate, 4mM spermidine, 0.5% NP-40). Mix short adapter, bridging linker with Tn5, and then incubate at room temperature for 20 minutes to produce Tnp complex. Add the complex to cells and  mix gently, then incubate at 37°C for 4 hours with interval shaking. Stop the reaction by adding EDTA, then reverse crosslinking by incubating at 65°C overnight.   Purify genomic DNA, and fill-in gaps with T4 DNA polymerase. Remove free bridging linker by AMPure XP beads. Then, digest purified DNA with restriction enzymes MluCI/NlaIII, and enrich biotin-labeled DNA fragments with streptavidin beads. Perform adapter ligation on beads, and wash away free adapters. Run PCR with illumina multiplexing indexed primers. Libraires are purified and submitted for paired-end sequencing.