Chromatin Immunoprecipitation for Chromatin Interaction Analysis Using Paired-End-Tag (ChIA-PET) Sequencing in Tadpole Tissues.

Proper gene expression involves communication between the regulatory elements and promoters of genes. Because regulatory elements can be located over a large range of genomic distances (from as close as a few hundred bp to as much as several Mb away), contact and communication between regulators and the core transcriptional machinery at promoters are mediated through DNA looping. Today, chromosome conformation capture (3C)-based methods efficiently probe chromosome folding in the nucleus and thus provide a molecular description of physical proximity between enhancer(s) and their target promoter(s). One such method, chromatin interaction analysis using paired-end-tag (ChIA-PET) sequencing, is a leading high-throughput method for detection of genome wide chromatin interactions. Briefly, the method involves cross-linkage of chromatin (-DNA) fibers in cells in situ, fragmentation of the fixed chromatin-DNA complexes by sonication, followed by enrichment of the chromatin complexes with a dedicated antibody through the process of immunoprecipitation (IP). Next, application of the ChIA-PET protocol followed by deep sequencing and mapping of reads to the reference genome reveals both binding sites and remote chromatin interactions mediated by the protein factors of interest. The method detailed here focuses on ChIP sample preparation and can be completed in ∼5 d. The ChIA-PET method is detailed in an associated protocol. Because not all chromatin immunoprecipitation protocols are suitable for ChIA-PET, it is important to strictly follow this procedure before performing the ChIA-PET protocol.