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Sister chromatid cohesion is mediated by individual cohesin complexes

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Feb 22, 2024 version files 88.95 GB

Abstract

Eukaryotic genomes are organized by loop extrusion and sister chromatid cohesion, both mediated by the multimeric cohesin protein complex. Understanding how cohesin holds sister DNAs together, and how loss of cohesion causes age-related infertility in females, requires knowledge as to cohesin’s stoichiometry in vivo. Using quantitative super-resolution imaging, we identify two discrete populations of chromatin-bound cohesin in post-replicative human cells. While most complexes appear dimeric, cohesin localized to sites of sister chromatid cohesion and associated with Sororin is exclusively monomeric. The monomeric stoichiometry of Sororin:cohesin complexes demonstrates that sister chromatid cohesion is conferred by individual cohesin rings, a key prediction of the proposal that cohesion arises from their co-entrapment of sister DNAs.