These are three biological replicates. HeLa cells were crosslinked on separate days. In each case, a matched total from the same crosslinking was produced in parallel. Amplicons were made from each and hybridized onto ENCODE region tiling arrays. Two color arrays were used; ChIP was red, Total was green. Goal was determination of E2F1 binding sites in HeLa cells by using ChIP-chip methodology. See Farnham Lab website for downloadable protocol for ChIP or supplementary file (Chip_protocol.txt) below. NimbleGen performed all array processing. See NimbleGen website for information on array procedures.