Transcription factor that binds to GC box promoter elements. Selectively activates mRNA synthesis from genes containing tandem repeats of GC boxes but represses genes with a single GC box. Acts as an epidermal circadian transcription factor regulating keratinocyte proliferation (PubMed:22711835). Interacts with ZZEF1. Epidermis (at protein level). Expression is highly sensitive to glucocorticoids and shows diurnal expression patterns. A strong induction of expression seen during keratinocyte differentiation in a cortisol dependent manner. Belongs to the Sp1 C2H2-type zinc-finger protein family.