RAD21 and cancer: In contrast, in three different cancer cell lines, HAP1 (Haarhuis et al., 2017), HCT116 (Rao et al., 2017), and HeLa (Wutz et al., 2017), we did not observe obvious punctate interactions between polycomb chromatin domains in control cells, and these sites did not interact following removal of SCC1 (HCT116 and HeLa) or removal of the cohesin loader component SCC4 (HAP1).