Gene Product Sp1 Transcription Factor Sufficient MESH:D016329 SCDO:1000392 Promoter-specific RNA polymerase II transcription factor that binds to the GC box, one of the upstream promoter elements, in mammalian cells. The binding of Sp1 is necessary for the initiation of transcription in the promoters of a variety of cellular and viral GENES. Transcription Factor, Sp1