Identification of physical interactions between genomic regions by enChIP-Seq
Physical interactions between genomic regions play critical roles in the regulation of genome functions, including gene expression. However, the methods for confidently detecting physical interactions between genomic regions remain limited. Here, we demonstrate the feasibility of using engineered DNA-binding molecule-mediated chromatin immunoprecipitation (enChIP) in combination with next-generation sequencing (NGS) (enChIP-Seq) to detect such interactions. In enChIP-Seq, the target genomic region is captured by an engineered DNA-binding complex, such as a CRISPR system consisting of a catalytically inactive form of Cas9 (dCas9) and a single guide RNA (sgRNA). Subsequently, the genomic regions that physically interact with the target genomic region in the captured complex are sequenced by NGS. Using enChIP-Seq, we found that the 5HS5 locus, which regulates expression of the {beta}-globin genes, interacts with multiple genomic regions upon erythroid differentiation in the human erythroleukemia cell line K562. Genes near the genomic regions inducibly associated with the 5HS5 locus were transcriptionally up-regulated in the differentiated state, suggesting the existence of a coordinated transcription mechanism directly or indirectly mediated by physical interactions between these loci. Our data suggest that enChIP-Seq is a potentially useful tool for detecting physical interactions between genomic regions in a non-biased manner, which would facilitate elucidation of the molecular mechanisms underlying regulation of genome functions.