Rad21 is the core subunit of cohesin complex in directing genome organization

In eukaryotes, the nuclear chromatin in the interphase is a hierarchical organization. Previous studies have suggested that cohesin-DNA interactions play important architectural functions for chromatin structure in the interphase. In this study, we applied super-resolution imaging, single-molecule imaging to measure the distribution of cohesin subunits. Hi-C and RNA-seq were used to reveal the 3D genome structures alterations and the relationship with breast cancer upon Rad21 up-regulation. Hi-C experiment showed that the contact frequency of short distance was increased while that of long distance was decreased in the absence of Rad21 up-regulation. Chromatin interactions between A and B compartments increased and compartmentalization strength was reduced significantly upon Rad21 up-regulation. Correspondingly, accumulated contacts were shown at TAD corners and inter-TAD interactions increased. These observations support cohesin loop extrusion model and lead us to propose the unique role of Rad21-loader interaction in cohesin loading and further cohesin extrusion. Moreover, we combined transcriptome changes and chromatin structure alterations upon Rad21 up-regulation and revealed the correlation between Rad21 and breast cancer by affecting chromatin architecture. Overall design: Analysis of 3D genome architecture and gene expression data in control and Rad21 overexpression HeLa cell lines.