Figure 6. RNA-polymerase-II (Poll-II) associations at the activated rhodopsin gene (Rho). A: Pol-II ChIP-on-chip data viewed with the IGB program around the Rho transcription start site (TSS), including the rhodopsin proximal promoter region (RPPR) and the upstream rhodopsin enhancer region (RER). The Rho gene was not preloaded with inactive Pol-II in P2 neural retina before expression in maturing photoreceptors. Two regions of maximum Pol-II signal corresponded to the RPPR and RER regions of the promoter. The FIZ1 ChIP signal maximum also corresponded to the RPPR. B: While the RPPR is sufficient for gene activation, the RER is required for maximum activity. Transcription factors shown to enhance Rho expression can bind to sequences in the RER, about 2,500 bp upstream of the RPPR. The Pol-II ChIP-on-chip pattern is consistent with a DNA loop model where distal enhancer regions (the RER) become integrated with the gene’s RPPR in the full enhanceosome complex.