RB is a cell cycle-regulated repressor of cohesin-dependent loop formation

Chromatin organization and cell cycle are tightly intertwined in eukaryotes, but the underlying mechanisms remain unclear. We investigated how the retinoblastoma protein (RB), a key cell cycle regulator localized to chromatin insulators, influences chromatin architecture. Utilizing chromosome conformation capture, we revealed that RB loss increased the number and size of cohesin-dependent loops and strengthened topologically associating domains (TADs). Mechanistically, RB regulated the chromatin distribution of cohesin, which extensively colocalized with RB in the human genome. Active RB evicted cohesin from RB-bound TAD boundaries and repressed insulator activity, thereby enhancing the expression of non-E2F target genes central to cell adhesion. We identify RB's centrality in the interplay between cell cycle and chromatin organization and propose a novel RB function in safeguarding chromatin architecture and thereby transcription.