RUNX1-Mediated Binding Site Directed DNA Demethylation is a Novel Mechanism of Hematopoietic Gene Activation.

RUNX1 (also known as AML1) is a key transcription factor for definitive hematopoietic stem cell development and following hematopoietic cell linage specifications, in which chromatin- or epigennome-mediated regulation by RUNX1, particularly regulation of DNA methylation status, is proposed to be involved in addition to its direct gene expression regulation. However, how RUNX1 regulates DNA methylation status and its role in the hematopoiesis remain to be elucidated. Here we first demonstrated that RUNX1 induces RUNX1 binding site directed DNA demethylation across the whole genome. HaloTag-based pull-down assay revealed associations of RUNX1 with active DNA demethylation related proteins such as TET, TDG or GADD45A, suggested that the RUNX1-mediated DNA demethylation is active DNA demethylation mechanism. Additional combinatorial overexpression of TET and TDG enlarged the RUNX1-mediated DNA demethylation, supporting what RUNX1-mediated DNA demethylation is active DNA demethylation. These results strongly suggested that RUNX1-mediated DNA demethylation is achieved by recruiting those proteins involved in active DNA demethylation. Finally, we found that the RUNX1-mediated demethylation predominately targets and activates hematopoietic genes whose promoter regions are demethylated during hematopoiesis. Collectively, our insight suggested that RUNX1-mediated binding site directed DNA demethylation is a novel mechanism of hematopoietic gene activation. Bisulphite converted DNA from the 6 samples were hybridised to the Illumina Infinium 450k Human Methylation Beadchip