Gene regulation and priming by Topoisomerase IIα in embryonic stem cells [ChIP-chip]

Topoisomerases are essential for resolving topological problems in the genome, while their function in gene regulation, especially during cellular differentiation, remains elusive/unknown. We reveal that the expression of two Topo II isoforms, Top2α and Top2β, is characteristic of dividing and postmitotic tissues, respectively. In embryonic stem cells, Top2α preferentially binds to promoters embedded in an active chromatin environment. Inhibition of Top2α activity results in misregulation of target gene expression that accompanies accumulation of double-strand breaks. Common targets of Top2α and Top2β are housekeeping genes while their unique targets are involved in proliferation/pluripotency and neurogenesis (Can we say this as this might be because we are driving neurons from ES cells), respectively. Moreover, a small subset of Top2α targets exhibit bivalent chromatin state that is resolved upon differentiation concomitant with their activation and occupancy by Top2β, a feature further observed for large lengthlong genes. These findings suggest that Top2α not only contributes to stem cell transcriptome regulation but may also prime developmental genes for subsequent activation by Top2β. Chromatin IP was performed with Top2α antibodies in WT ES cells and hybridized to custom designed tiling array.