The NSMCE2 (NSE2, MMS21) subunit of the SMC5/6 complex SUMOylates the RAD21 and STAG2 subunits of cohesin with SUMO1 (Potts et al. 2006 supplementary data, reviewed in Stephan et al 2011). RAD21 (SCC1) is SUMOylated at several lysines (Wu et al. 2012). SUMOylation of RAD21 occurs during DNA damage repair and is necessary for sister chromatid recombination (Wu et al. 2012).