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. Analysis of 3D genome architecture and gene expression data in control and Rad21 overexpression HeLa cell lines.