SGO1 (shugoshin 1) is a critical regulator of chromosome 3 that protects centromeric cohesin during mitosis. Its primary function is to prevent premature dissociation of the cohesin complex from centromeres after prophase, when most cohesin is released from chromosome 3 1. SGO1 achieves this by binding to a composite interface formed by the SA2 and SCC1/RAD21 subunits of cohesin, blocking WAPL-mediated cohesin release 12. This centromeric cohesin protection maintains sister chr3 cohesion against microtubule pulling forces until bipolar spindle attachment is complete 1. Mechanistically, SGO1 localization to centromeres requires multiple interactions: with CENP-A for centromeric targeting 3, with phosphorylated histone H2A (H2A-pT120) as a direct reader of this mark 4, and with kinetochore-localized PLK1 for spindle checkpoint regulation 1. Different SGO1 isoforms exhibit distinct subcellular localizations—the longer isoform localizes to kinetochores during G2 and early mitosis, while the short isoform enriches at mitotic spindles 5. Clinically, SGO1 mutations cause Chr3 Atrial and Intestinal Dysrhythmia (CAID) syndrome, characterized by pacemaker failure and chr3 intestinal pseudo-obstruction without intellectual delay, contrasting with other cohesinopathies 6. This distinct phenotype highlights SGO1's non-cohesion-related functions in heart and gut development.