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. 2007 Sep 7;35(18):6137–6149. doi: 10.1093/nar/gkm656

Figure 7.

Figure 7.

A proposed model of transcriptional regulation of HDC is shown by different nuclear factors at the upstream GC box in the promoter. Sp1 has been shown to activate the promoter through this element. Gastrin activates HDC gene expression through both downstream gastrin responsive elements and the upstream GC box. Our published data also suggest that YY1 and SREBP-1a form a complex to compete Sp1 in binding the GC box, resulting in the transcriptional inhibition. The double line with arrow indicates that the downstream GAS-RE is required for this inhibition. Published data and the data presented here suggest that gastrin activates Sp1. Competition between Sp1 and KLF4 on the upstream GC box of the HDC promoter then decreases association of KLF4-Tip60-HDAC7 repressive complexes with the promoter, resulting in the upregulation of HDC gene expression. The relationship between YY1/SREBP-1a complex and KLF4/Tip60/HDAC7 complex remains to be determined.