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SummaryCondensin complexes are evolutionarily conserved molecular motors that translocate along DNA and form loops. While condensin-mediated DNA looping is thought to direct the chain-passing activity of topoisomerase II to separate sister chromatids, it is not known if topological constraints in turn regulate loop formation in vivo. Here we applied auxin inducible degradation of topoisomerases I and II to determine how DNA topology affects the translocation of an X chromosome specific condensin that represses transcription for dosage compensation in C. elegans (condensin DC). We found that both topoisomerases colocalize with condensin DC and control its movement at different genomic scales. TOP-2 depletion hindered condensin DC translocation 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 expressed gene bodies. Both TOP-1 and TOP-2 depletions resulted in X chromosome transcriptional upregulation indicating that condensin DC translocation at both scales is required for its function in gene repression. Together the distinct effects of TOP-1 and TOP-2 on condensin DC distribution revealed two distinct modes of condensin DC association with chromatin: long-range translocation that requires decatenation/unknotting of DNA and short-range translocation across genes that requires resolution of transcription-induced supercoiling.

Nutrient uptake by plant roots seriously affects the growth and yield of maize. AUX/IAA encoding genes play an important role in auxin signal transduction and regulating the growth of plant roots.In this study, AUX/IAA gene ZmLLG1 was cloned from maize. The expression level of the ZmLLG1 gene in different tissues was detected by qRT-PCR, and ZmLLG1 was found to be overexpressed in the roots of maize. Arabidopsis thaliana and mutant maize were both analyzed by statistical method. A yeast two-hybrid experiment, BiFC experiment and pull-down experiment were used to verify the interactions between the protein and ZmLLG1.The CoDing Sequence (CDS) of ZmLLG1 is 684 bp and encodes a protein composed of 227 amino acids. A subcellular localization analysis confirmed that ZmLLG1 was localized in the nucleus. The ZmLLG1 gene was expressed in all tissues of maize, but its expression level was highest in the root. The root length and number of lateral roots of zmllg1 mutant maize were much lower than those of wild-type B73 maize, and ZmLLG1 was responsive to auxin. The yeast two-hybrid assay, BiFC experiment and pull-down assay showed that ZmLLG1 could interact with ZmARF5, ZmARF7, and ZmARF25 to regulate the growth and development of the maize root system. Keywords AUX/IAA, Root, ARF, Maize mutant, Protein