Mechanism of repression of GM-CSF activated transcription by 1,25(OH)2D3. Unlike most mechanisms involved in 1,25(OH)2D3 mediated effects on transcription that require the VDR/RXR heterodimer, VDR bound to 1,25(OH)2D3 (VDRD3 in B) acts as a monomer on the GM-CSF promoter and competes with NFAT for binding to a composite NFAT AP1 site (composite site is shown in A). VDR bound to 1,25(OH)2D3 also stabilizes the binding of Fos-Jun heterodimer by direct interaction with cJun (B). These two events result in 1,25(OH)2D3 mediated transcriptional repression of GM-CSF (Adapted from Towers and Freedman, 1998)