一、技術簡介

染色質免疫沉淀法（Chromatin immunoprecitation，ChIP）是研究體內DNA與蛋白質相互作用的重要工具。它可以靈敏地檢測目標蛋白與特異DNA片段的結合情況，還可以用來研究組蛋白與基因表達的關系。它能真實、完整地反映結合在DNA序列上的調控蛋白，是目前確定與特定蛋白結合的基因組區域或確定與特定基因組區域結合的蛋白質的最好方法。
基本原理是在活細胞狀態下固定蛋白質－DNA復合物，并將其隨機切斷為一定長度范圍內的染色質小片段，然后通過免疫學方法沉淀此復合體，特異性地富集目的蛋白結合的DNA片段，通過對目的片斷的純化與檢測，從而獲得蛋白質與DNA相互作用的信息。它能真實、完整地反映結合在DNA序列上的調控蛋白，是目前確定與特定蛋白結合的基因組區域或確定與特定基因組區域結合的蛋白質的一種很好的方法。
   

二、實驗步驟

1、 甲醛交聯
2、 超聲打碎DNA
3、 免疫沉淀
4、 消化蛋白質及解交聯
5、 PCR擴增目的啟動子片段
 

三、應用實例

Fig1: ChIP analysis to detect in vivo binding of c-Jun to the dp5 promoter.
CGNs maintained in 25 or 5 K medium for 4 h were treated with formaldehyde to cross-link endogenous proteins and DNA. Samples of sonicated and purified chromatin were immunoprecipitated with a rabbit c-Jun antibody or a normal rabbit IgG. A, chromatins were sonicated into fragments about 0.5 kb in length. B, Western blotting analysis (WB) was performed using a monoclonal c-Jun antibody to demonstrate the immunoprecipitation (IP) specificity and efficiency and analyze c-Jun cellular protein levels. C, left, DNA isolated and purified from immunoprecipitated material was amplified by PCR with primers to amplify a 169-bp fragment of dp5 promoter spanning the ATF site (top), and a 173-bp fragment encompassing a canonical ATF sequence (TRE-jun2 site) located in the c-jun promoter was also amplified (bottom). The amplified PCR fragments were analyzed on 2% agarose gel.C, right, equal amounts of total genomic DNA (Input) were used for immunoprecipitation in each condition. Data are representative of three separate experiments.