Interrogation of the Dynamic Properties of Higher-Order Heterochromatin Using CRISPR/dCas9

Eukaryotic chromosomes feature large regions of compact, transcriptionally-repressed heterochromatin hallmarked by the presence of Heterochromatin Protein 1 (HP1) family members. HP1 proteins play multi-faceted roles in directly shaping the properties of heterochromatin, and in vivo , HP1 tethering to individual gene promoters leads to epigenetic modifications and gene silencing. However, emergent properties of HP1 at supranucleosomal scales have been difficult to study in cells due to a lack of appropriate tools. Here, we develop CRISPR-Engineered Chromatin Organization (EChO), a novel approach for combining live cell CRISPR-based imaging with inducible and reversible large-scale recruitment of heterochromatin components to native chromatin in human cells. Using CRISPR-EChO, we demonstrate that human HP1α binding across tens of kilobases of genomic DNA leads to formation of novel contacts with other heterochromatin regions and reversibly compacts chromatin from a diffuse to condensed state. The condensed chromatin state exhibits delayed disassembly kinetics and represses transcription across over 600 kilobases. Collectively, these findings support a polymer model of HP1α-mediated chromatin regulation and highlight the utility of CRISPR-EChO in studying and manipulating supranucleosomal chromatin organization in living cells. 3 replicates of ABA-treated and Control DMSO-treated samples. Paired end fastq files as well as processed bigwig files are uploaded.