Rapid movement and transcriptional re-localization of human cohesin on DNA.

Iain F Davidson,Pim J Huis In 'T Veld,Jan‐Michael Peters,Maria Ocampo‐Hafalla,Alipasha Vaziri,Frank Uhlmann,David A Cisneros,Florian Weissmann,Gabriele Litos,Maciej P Zaczek,Rene Ladurner,Maxim I Molodtsov,Daniela Goetz

doi:10.15252/embj.201695402

Abstract

The spatial organization, correct expression, repair, and segregation of eukaryotic genomes depend on cohesin, ring‐shaped protein complexes that are thought to function by entrapping DNA. It has been proposed that cohesin is recruited to specific genomic locations from distal loading sites by an unknown mechanism, which depends on transcription, and it has been speculated that cohesin movements along DNA could create three‐dimensional genomic organization by loop extrusion. However, whether cohesin can translocate along DNA is unknown. Here, we used single‐molecule imaging to show that cohesin can diffuse rapidly on DNA in a manner consistent with topological entrapment and can pass over some DNA‐bound proteins and nucleosomes but is constrained in its movement by transcription and DNA‐bound CCCTC‐binding factor (CTCF). These results indicate that cohesin can be positioned in the genome by moving along DNA, that transcription can provide directionality to these movements, that CTCF functions as a boundary element for moving cohesin, and they are consistent with the hypothesis that cohesin spatially organizes the genome via loop extrusion.

Highlights

Cohesin complexes mediate sister chromatid cohesion, which is essential for proper chromosome segregation in dividing cells, and have important roles in DNA damage repair, recombination, higher-order chromatin structure, and gene regulation in both proliferating and quiescent cells
We first reconstituted the binding of recombinant human cohesin composed of Smc1, Smc3, Scc1, and Stag1 (Fig 1A) to DNA, using a bulk assay developed by Murayama and Uhlmann (Murayama & Uhlmann, 2014)
This binding was greatly reduced if DNA had been linearized (Fig 1B) or if a form of cohesin was used in which a recognition site for tobacco etch virus (TEV) protease engineered into Scc1 had been cleaved (Fig 1C and D)

Summary

Introduction

Cohesin complexes mediate sister chromatid cohesion, which is essential for proper chromosome segregation in dividing cells, and have important roles in DNA damage repair, recombination, higher-order chromatin structure, and gene regulation in both proliferating and quiescent cells (reviewed in Merkenschlager & Nora, 2016). In vivo, this interaction depends on ATP hydrolysis by Smc and Smc, and on the Nipbl/Mau ( known as Scc2/Scc4) cohesin loading complex (Ciosk et al, 2000; Arumugam et al, 2003; Weitzer et al, 2003; Gillespie & Hirano, 2004; Takahashi et al, 2004; Watrin et al, 2006; Hu et al, 2011; Ladurner et al, 2014) and can be reversed either by the cohesin-associated protein Wapl or the protease separase.

Methods

Results

Conclusion