ESR1 and breast cancer: It is believed that the promoter region of the gene encoding ERα is subjected to greater loading by RNA polymerase II (RNAPII) and TATA-binding protein (TBP), thus increasing its transcription due to the greater abundance of basic transcription factors; due to such increased loading, SIRT1 maintains the expression of ERα in cells (at least in the breast cancer cells with which the cited studies were performed, i.e., MCF7 and T47D), enables the expression of all estrogen-dependent genes dependent on Erα, and determines the high survival rate of breast cancer cells in vitro [51].