Updated publication reference for PubMed record(s): 33929514. The accurate segregation of chromosomes during mitosis relies on the attachment of sister chromatids to microtubules from opposite poles, called biorientation. Sister chromatid cohesion resists microtubule forces, generating tension which provides the signal that biorientation has occurred. How tension silences the surveillance pathways that prevent cell cycle progression and correct erroneous kinetochore-microtubule remains unclear. Here we identify SUMOylation as a mechanism that promotes anaphase onset upon biorientation. SUMO ligases modify the tension-sensing pericentromere-localized chromatin protein, shugoshin, to stabilize bioriented sister kinetochore-microtubule attachments and allow entry into anaphase. SUMOylation of shugoshin prevents binding to protein phosphatase 2A (PP2A), while enhancing chromosome passenger complex (CPC) interaction and removal from centromeres. Dissociation of the shugoshin-PP2A interaction is important for stabilizing sister kinetochore biorientation. Therefore, SUMOylation modulates protein interactions within pericentromeres to allow a signalling switch in response to biorientation.