Repression of DNMT1 promoter activity by methylated E2F1 motif. Ai, comparative analysis of E2F1 motif methylation between BRCA1-mutated breast cancer and adjacent normal breast tissues. Aii, relationship between DNMT1 protein expression and promoter methylation in BRCA1-mutated breast cancer and adjacent normal breast tissues (U; unmethylated group, n = 46, M; methylated group, n = 39). Bi, the schematic shows that the nucleotide sequence of consensus E2F1 motif (Con.E2F1) was point mutated at position +182 (C to T) to generate the Mut.E2F1. Bii, 293 T cells, and 15 primary non-mutated and BRCA1-mutated breast cancer and their normal breast cells were transfected with Con.E2F1 and Mut.E2F1. 24 hours after transfection, whole-cell extracts were analyzed for luciferase activity. Each experiment was repeated four times for 293 T cells and primary breast cells of each patient. Bar graphs show mean ± SD. Ci, the schematic represents the selected nucleotide sequence containing the E2F1 motif, with or without a methyl group at the fifth position of the cytosine pyrimidine ring at position +182. Cii and Ciii, The CD spectra of the selected nucleotide sequence in the presence of 100 mM Na+ or 100 mM K+ are shown.