Since paclitaxel is a cell cycle inhibitor, and CHFR, as a ubiquitin ligase (E3), is regarded as involved in a checkpoint regulating entry to mitosis and to arrest cancer cells at the G2-M phase after treatment with microtubule inhibitors, like paclitaxel24,25, we checked CHFR as a candidate for UBC13’s downstream modulator, and found that CHFR expression was synchronously decreased with UBC13 decline in both types of cells upon exposure to paclitaxel for 24 h (Fig. 3a, b). The gene discussed is CHFR; the disease is cancer.