Nuclear exosome targeting complexes modulate cohesin binding and enhancer-promoter interactions in 3D

Three-dimensional long-range contacts between enhancers and promoters are thought to be largely determined by loop extrusion driven by the cohesin complex and insulator factors.

However, recent evidence also suggests a role for noncoding RNAs (ncRNAs), such as enhancer-associated RNAs (eRNAs) and promoter upstream transcripts (PROMPTs), in shaping enhancer-promoter connectivity. While nuclear RNA exosome, together with targeting complexes, PAXT and NEXT, control the decay of ncRNAs, it has not yet been determined whether these complexes regulate 3D contacts. Chromatin recruitment maps of ZCCHC8 (NEXT), ZFC3H1 (PAXT) and MTR4 helicase revealed that these factors that associate with sites of enhancer-promoter interactions. Depletion of NEXT, PAXT or MTR4 induced the accumulation of ncRNAs, notably enhancer-associated RNAs (eRNAs) and promoter upstream transcripts (PROMPTs). Strikingly, this further increased cohesin levels at sites accumulating ncRNAs. Chromatin conformation capture analysis revealed that MTR4 modulates the 3D long-range contacts between enhancers with their distant TSS targets. Upon loss of MTR4, contacts at anchor points increase while intraloop contacts decrease, suggesting that MTR4 facilitates loop extrusion. These data highlight a key interplay between cohesin-mediated enhancer-promoter interactions and the regulation of ncRNAs by nuclear RNA exosome that is consistent with a role for RNA in genome folding.

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