Performing Quantitative PCR after Chromatin Immunoprecipitation (ChIP) of Drosophila Antennal and Brain Samples.

Chromatin immunoprecipitation (ChIP) is a technique used to study specific protein-DNA interaction. Briefly, in this technique, antibodies to proteins of interest are used to isolate regions of DNA where these proteins bind. ChIP samples can be processed and analyzed in different ways. One of the approaches for assessing the results of ChIP experiments is quantitative PCR (qPCR). qPCR is used to quantitatively measure the amount of DNA fragments that have been isolated, reflecting the signal of specific proteins interacting with these fragments. This protocol describes both the "percent input" method and the "fold enrichment" method for ChIP-qPCR data analysis using Drosophila tissues as an example. The "percent input" method measures signals of DNA fragments against the input measurement. In contrast, the "fold enrichment" method quantifies the amplified signal strength relative to a background control. Because the quality of primers is critical for the reliability of ChIP-qPCR results, this protocol also describes how to measure primer amplification efficiency using Drosophila genomic DNA.