The T allele of rs1271572 down-regulated the activity of the ERβ promoter 0 N. A). The human breast cancer cells (MDA-MB-231, MCF-7, MDA-MB-468, BT-549 and ZR75-30) were transfected with the normalization control vector pRL and each of the pESR2-0 N-G-Luc, pESR2-0 N-T-Luc, pESR2-0 K-Luc (promoter 0 K) alone, or together with the YY1-specific siRNA oligos. Lucifease activities of these reporters were determined using the dual luciferase assay kit. B). Primary breast cancer cells (N1, N2 and N3) were transfected with the vectors as in A) and luciferase activity was determined. The figure represents the results of three independent experiments. *p <0.05;**p <0.01. Graphs show means + −S.E.M. (n =8). C). The human breast cancer cell lines (MDA-MB-231, MCF-7, MDAMB468, BT549 and ZR75-30) and the primary breast cancer cells (N1 and N2) were transfected with YY1-specific siRNA oligos and YY1 expression was examined by western blot. β-actin was used to confirm equal protein loading. Each lane was loaded with up to 30 μg of protein.