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New perspective on how loop extrusion mechanism works


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    Some questions:

    1. How is the kleisin–HAWK DNA-bound subcomplex and the hinge region is CTCF motif specific?
    2. Which force makes the kleisin–HAWK DNA-bound subcomplex go a direction by which the extrusion happens?
    3. Why cohesin SMC complexes have no such mechanism?
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      For the 1st question:

      It was shown before that C-terminus of CTCF protein interacts with cohesin complexes (probably with condensin too). So, TAD-inward motifs leads to a CTCF-cohesin interaction, if CTCF is bound, of course.

      For the 2nd question:

      In this paper, they proposed that a unidirectional movement can be achieved if two heads (subcomplexes) have different DNA-binding affinities. The weaker one will move forward upon separation, and the other will follow. However, I couldn’t find any explanation for a possible reverse movement, i.e. in the case of loop dissociation.

      For the 3rd, I don’t have an answer too :)