Chromatin immunoprecipitation (ChIP)is a powerful technique for studying protein-DNA interactions and mapping the localization of epigenetic histone modifications on DNA in cells. We have developed a quick and quantitative Q2ChIP assay for immunoprecipitation of histones and transcription factors from chromatin from low cell numbers (Dahl and Collas, 2007). Q2ChIP is a one-day ChIP assay which greatly simplifies the procedure, minimizes sample loss and enhances specificity. The Q2ChIP protocol can be found here. Further development of the assay led to a micro-ChIP protocol which enables ChIP of histones and transcription factors from as few as 100 cells (Dahl and Collas, 2008). Micro-ChIP is well suited for ChIP analysis of embryos, ES cells and small tissue biopsies. A protocol of the micro-ChIP assay has been published (Dahl and Collas, 2008) and can be found here. We have also recently applied microChIP from 1,000 cells to genome-wide promoter surveys of histone modifications, opening to door to comprehensive epigenetic investigations in scare cell samples or biopsies.
