簡要描述：Profound changes in patterns of gene expression can result from relatively small changes in the concentrations of sequence specific transcription factors. Synergistic interaction between factors bound to different sites within a transcriptional control region is supported by the work of Courey et al. (1989). Sp1 is a sequence specific transcription factor that recognizes GGGGCGGGGC and closely related sequences, which are often referred to as GC boxes. Sp1 binds to GC box promoters elements ａ