GLI1 and melanoma: At the same time, in Figure 4(b), the left images show the typical and atypical activation pathways of the HH signaling pathway in melanoma: SOX2 and BRD4 form a complex, and BRD4, by interacting with acetylated histones in the proximal region of the GLI1 promoter, induces RNA polymerase 2 activity and transcriptional activation of GLI1.