Figure 6.

Schematic diagrams illustrating the function of Element I in NGB gene transcription regulation. (A) In NGB-expressing cells, a chromatin loop is formed between the NGB promoter and Element I. The loop brings GATA-2 on Element I and Sp1 on the hypomethylated NGB promoter (open circle) in close proximity and activates transcription. (B) In cells not expressing NGB, the promoter of NGB gene is hypermethylated (filled circles) and binding of Sp1 and Sp3 is inhibited. This impairs the interaction between the promoter and Element I. The formation of looping may also be affected by competition between GATA-2 and -3 for the binding sites within Element I.