ESR1 and breast cancer: qChIP-dependent promoter walk experiments showed that, in breast cancer cells, ERα was mainly enriched in the −800 to −200 section of the TRIM21 promoter (Fig. 6K and Supplementary Fig. 6C), MTA1 was mainly enriched in the −1 400 to −500 region of the TRIM21 promoter (Fig. 6K).