A Central Role for PRC1 in Shaping the 3D Nuclear Landscape

1. Loss of RING1B substantially disrupts nuclear architecture. 2. PRC1 mediated looping can occur at a Mb scale and is independent of CTCF. 3. Polycomb mediated looping is driven by canonical PRC1 complexes. 4. Trimeric PRC1-mediated interactions occur in vitro and in vivo. 5. Gene up-regulation does not directly lead to the loss of PRC1 loops. Hi-C analysis of WT, RING1B I53A and RING1B KO E14 mouse ES cells; 4 replicates for WT and 2 replicates each, for both mutants.