Transport of DNA within cohesin involves clamping on top of engaged heads by Scc2 and entrapment within the ring by Scc3.

James E Collier, Byung-Gil Lee, Maurici Brunet Roig, Stanislav Yatskevich, Naomi J Petela, Jean Metson, Menelaos Voulgaris, Andres Gonzalez Llamazares, Jan Löwe, Kim A Nasmyth

eLife 2020 Sep 15

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In addition to extruding DNA loops, cohesin entraps within its SMC-kleisin ring (S-K) individual DNAs during G1 and sister DNAs during S-phase. All three activities require related hook-shaped proteins called Scc2 and Scc3. Using thiol-specific crosslinking we provide rigorous proof of entrapment activity in vitro. Scc2 alone promotes entrapment of DNAs in the E-S and E-K compartments, between ATP-bound engaged heads and the SMC hinge and associated kleisin, respectively. This does not require ATP hydrolysis nor is it accompanied by entrapment within S-K rings, which is a slower process requiring Scc3. Cryo-EM reveals that DNAs transported into E-S/E-K compartments are 'clamped' in a sub-compartment created by Scc2's association with engaged heads whose coiled coils are folded around their elbow. We suggest that clamping may be a recurrent feature of cohesin complexes active in loop extrusion and that this conformation precedes the S-K entrapment required for sister chromatid cohesion. © 2020, Collier et al.

Citation

James E Collier, Byung-Gil Lee, Maurici Brunet Roig, Stanislav Yatskevich, Naomi J Petela, Jean Metson, Menelaos Voulgaris, Andres Gonzalez Llamazares, Jan Löwe, Kim A Nasmyth. Transport of DNA within cohesin involves clamping on top of engaged heads by Scc2 and entrapment within the ring by Scc3. eLife. 2020 Sep 15;9