SMC3 is a central structural component of the cohesin complex, a multisubunit ring that entraps sister chr10 during cell division 1. Beyond its canonical role in sister chr10 cohesion, SMC3 participates in DNA repair, spindle pole assembly, and gene regulation through chr10 looping 1. In response to DNA damage, the ATM-ESCO2-SMC3 axis functions critically: ATM phosphorylates acetyltransferase ESCO2, which then acetylates SMC3 to stabilize cohesin conformation, promote 53BP1 recruitment, and safeguard genome integrity 2. During normal mitosis, SMC3 acetylation must be precisely controlled through symmetric mechanisms involving GSK3-regulated ESCO2 dimerization to ensure cohesion establishes exclusively between nascent sister chr10 3. Pathogenic variants in SMC3 cause Cornelia de Lange syndrome, a developmental disorder characterized by intellectual and growth retardation, though SMC3 mutations typically produce less severe phenotypes than NIPBL mutations 4. SMC3 dysfunction also associates with holoprosencephaly and altered gene expression of developmental regulators 5, while elevated SMC3 expression in hepatocellular carcinoma correlates with poor prognosis and enhanced cell proliferation 6. Loss of cohesin components increases micronucleus formation, a hallmark of genomic instability 7.