All three protein levels were higher in human breast cancer cells than in the normal human breast epithelial cell line MCF-10A (Fig. 6a), and the expression of Eg5 has been reported to be upregulated by oestrogen in MCF-7 cells36, suggesting a role of the RNF20/40 complex and Eg5 in breast carcinogenesis. The gene discussed is RNF20; the disease is breast carcinoma.