Topoisomerases I and II facilitate the translocation of condensin DC in C. elegans [ChIP-Seq II]

Condensin complexes are evolutionarily conserved molecular motors from the structural maintenance of chromosomes (SMC) family, that use ATPase activity to translocate along DNA and form loops. Condensin and topoisomerase II (TOP-2) are essential for the structure and function of mitotic chromosomes. While condensin-mediated DNA looping is thought to direct TOP-2 chain-passing activity to separate sister chromatids, it is not known if TOP-2 in turn regulates loop formation. Here we used an X chromosome specific condensin that represses transcription for dosage compensation in C.elegans, to determine how DNA topology affects SMC translocation in vivo. We applied auxin-inducible degradation of topoisomerases I and II to determine their effect on condensin DC binding and function. We found that both topoisomerases colocalize with condensin DC and control its movement at different genomic scales. TOP-2 depletion hindered condensin DC spreading over long distances, resulting in accumulation around its X-specific recruitment sites and shorter Hi-C interactions. In contrast, TOP-1 depletion did not affect long-range spreading but resulted in accumulation of condensin DC within gene bodies, specially of highly expressed and long genes. Both TOP-1 and TOP-2 depletion resulted in X chromosome upregulation indicating that condensin DC translocation at both scales is required for its function in transcriptional repression. Together our work reveals distinct DNA topological requirements for two modes of condensin DC association with chromatin: long-range linear translocation that requires decatenation and unknotting of DNA and short-range binding to genes that requires resolution of transcription-induced supercoiling. ChIP-seq data in WT, controls and topoisomerases I and II depleted conditions . Depletion was performed by Auxin inducible degradation. All experiments were performed in two biological replicates. L2/L3 larvae were used for most experiments. TOP-2 ChIP-seq in embryos and adults are also included.