It is demonstrated that protein arginine methyltransferase 6 (PRMT6), poly(ADP‐ribose) polymerase 1 (PARP1), and the cullin 4 B (CUL4B)‐Ring E3 ligase (CRL4B) complex interact to form a transcription‐repressive complex that co‐occupies the core clock gene PER3 promoter, promoting the proliferation and metastasis of breast cancer by interfering with circadian rhythm oscillation. This evidence concerns the gene CUL4B and breast cancer.