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. 2021 Feb 22;9:618586. doi: 10.3389/fcell.2021.618586

FIGURE 1.

FIGURE 1

CCCTC-binding factor (CTCF) mainly binds to the DNA polymerase delta 1, catalytic subunit (POLD1) promoter in two sites. (A) ENCODE database analysis showing potential CTCF-binding sites in the POLD1 promoter. (B) The JASPAR database predicted five higher score binding sites of CTCF to the POLD1 promoter, and the mutations of the two CTCF-binding sites were designed. (C) The binding sites of CTCF to the POLD1 promoter were analyzed by chromatin immunoprecipitation (ChIP) assay in lymphocyte cells (n = 40). *P < 0.05 vs. IgG-negative control group. (D) Luciferase activity assay demonstrated that the CTCF led to an increase in POLD1 promoter activity and that mutation of site 3 or 4 greatly reduced promoter activity in HEK293T cells (n = 3). **P < 0.01, ***P < 0.005 vs. POLD1 promoter wild type (WT) + CTCF. ###P < 0.001 vs. POLD1 promoter WT. Data were analyzed using Student’s t-test, and data are shown as mean ± SEM, with three independent experiments in each group.