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. 2016 Nov 22;11(11):e0166438. doi: 10.1371/journal.pone.0166438

Fig 3. Schematic representation of the ChIP-seq spike-in protocol.

Fig 3

ChIP-seq spike-in reactions are set up by adding the test chromatin of interest (human or other), the target antibody of interest, a small portion of D. melanogaster chromatin and the D. melanogaster-H2Av-specific antibody. The D. melanogaster spike-in chromatin is added in equal amounts and the H2Av antibody functions to pull down a small portion of the D. melanogaster chromatin in each reaction. After sequencing, tags are mapped to the genome corresponding to the test chromatin as well as to the D. melanogaster genome. The total number of tags uniquely mapping to the D. melanogaster genome are counted for each sample and used to generate correction factors (DMSO tags/inhibitor tags). The test chromatin tag counts are then normalized using the correction factors.