Suppression of BUB3 or treatment with reversine significantly decreased the number of polyploid cells (Figure S8A,B, Supporting Information), chromosome bridge frequency (Figure S8C,D, Supporting Information), and micronucleus rate (Figure S8E,F, Supporting Information) in HCT116 cells overexpressing YY2, which is likely due to the suppression of SAC activity to near wild‐type level in these cells as shown in Figure S5F,G (Supporting Information) Together, our results clearly show that both YY2 knockout and overexpression induced CIN. This evidence concerns the gene YY2 and cervical squamous intraepithelial neoplasia.