Cohesin is functionally required for correct estrogen-induced cell cycle progression. (A) Following RNAi-mediated knockdown of RAD21 and CTCF, cell cycle distributions after vehicle or estrogen treatment were assessed by propidium iodide staining followed by flow cytometry. (B) The percentage of cells in G0/G1 (black bars) and S/G2/M (gray bars) phases were quantitated after 24 h of vehicle or estrogen treatment (mean of n = 2; error bars, ±SD; *, t-test P-value ≤ 0.001). In vehicle-treated cells, suppression of CTCF caused a doubling of the cells in S/G2/M phases, compared with mock treatment. After 24 h of estrogen treatment, the removal of the cohesin subunit RAD21 caused a decrease in the number of cells that have transitioned to S/G2/M, indicating reduced cell-cycle progression. Removal of CTCF again enhanced entry into S/G2/M, but not with statistical significance.
