RAD21 and cancer: For example, mutations of the cohesin subunit STAG2 in acute myeloid leukemia induce longer chromatin loops and intermixing of compartments;14 recurrent cancer mutations in the cohesin subunit SMC1A result in impaired chromatin loops and gene expression;18 and reduced expression of the cohesin subunit Rad21 alters intrachromosomal interactions and creates an active transcriptional environment for cancer genes.16