FIGURE 16-2 Induction of a particular gene by a transcription factor depends not only on binding sites for the factor, but also on the gene’s epigenetic state and on the presence of master transcription factors and other nuclear proteins. Any given activated transcription factor has multiple sites on the chromosomal DNA to which it can potentially bind (green), but in any given cell it will bind only to those sites that are in an “open chromatin” conformation and in which specific master transcription factors or other cell-specific proteins (here colored blue and red, respectively) are bound to adjacent sites on the DNA. Other potential transcription factor binding sites are adjacent to binding sites for other master transcription factors (yellow) that are not expressed in this cell type, and thus the transcription factor will not bind to those sites.