Chromatin architecture mapping by multiplex proximity tagging.

Chromatin plays a pivotal role in genome expression, maintenance, and replication. To better understand chromatin organization, we developed a novel proximity-tagging method which assigns unique DNA barcodes to molecules that associate in 3D space. Using this method - Proximity Copy Paste (PCP) - we mapped the connectivity of individual nucleosomes in . We show that chromatin is predominantly organized into regularly spaced nucleosome arrays whose properties differ according to transcriptional activity. Additionally, by mapping long-range, multi-way interactions we provide evidence that metaphase chromosomes are compacted by arrayed cohesin hubs. Using single-molecule nuclease footprinting data we define distinct chromatin states within a mixed population to show that noncanonical nucleosomes are a stable feature of chromatin. PCP is a versatile method allowing the connectivity of individual molecules to be mapped at high-resolution.