Locus-specific chromatin profiling of evolutionarily young transposable elements [HiChIP]

Despite a vast expansion in the availability of epigenomic data, our knowledge of the chromatin landscape at interspersed repeats remains highly limited by difficulties in mapping short-read sequencing data to these regions. In particular, little is known about the locus-specific regulation of evolutionarily young transposable elements (TEs), which have been implicated in genome stability, gene regulation and innate immunity in a variety of developmental and disease contexts. Here we propose an approach for generating locus-specific protein-DNA binding profiles at interspersed repeats, which leverages information on the spatial proximity between repetitive and non-repetitive genomic regions. We demonstrate that the combination of Hi-ChIP and a newly developed mapping tool (PAtChER) yields accurate protein enrichment profiles at individual repetitive loci. Using this approach, we show that young TEs display locus- and tissue-specific chromatin profiles in both mice and humans. Insights gained using our method will be invaluable for dissecting the molecular determinants of TE regulation and their impact on the genome. Methylated DNA was immunoprecipitated from Hi-C libraries, and ends were mapped using a pipeline (PAtChER) that uses 3D information to map repetitive reads, producing ChIP-like profiles.