VDR ChIP-seq in human monocytic THP-1 cell line

Calcitriol, specific VDR agonist, treatment augmented the heterodimerization between VDR and RXR and we wanted to investigate its impact on VDR binding to genomic regions. ChIP-seq experiment was carried out in human monocytic THP-1 cell line under either vehicle, 1:1 DMSO-ethanol, or calcitriol (100 nM) treatment conditions.Our finding is that calcitriol has both stimulatory and inhibitory effect on VDR binding depending on the presence of its specific response element (VDRE), or a less specific nuclear receptor (NR) half-site or "none", where neither a VDRE nor an NR half-site sequence could be mapped. Upon calcitriol activation, VDRE-containing genomic regions showed considerably higher occupancies on average than in the control, vehicle-treated sample. A similar induction, but to a much lesser extent, was detected for the NR half-site-containing regions. In contrast, genomic regions not containing any of these specific response elements did not show any induction upon calcitriol treatment. We can conclude that ligand-induced heterodimerization and binding of the NR to its response elements are correlated events.