Gene regulation and priming by Topoisomerase IIα in embryonic stem cells [RNA-Seq]

Topoisomerases are essential for resolving topological problems in the genome, while their function in gene regulation, especially during cellular differentiation, remains unknown. We reveal that the expression of two Topo II isoforms, Top2a and Top2ß, is characteristic of dividing and postmitotic tissues, respectively. In embryonic stem cells, Top2a preferentially binds to promoters embedded in an active chromatin environment. Inhibition of Top2a activity results in misregulation of target gene expression that accompanies accumulation of double-strand breaks. Common targets of Top2a and Top2ß are housekeeping genes while their unique targets are involved in proliferation/pluripotency and neurogenesis, respectively. Moreover, a subset of Top2a targets exhibit bivalent chromatin state that is resolved upon differentiation concomitant with their activation and occupancy by Top2ß, a feature further observed for long genes. These findings suggest that Top2a not only contributes to stem cell transcriptome regulation but may also prime developmental genes for subsequent activation upon differentiation.