TATA box
Even though the TATA box is present in many eukaryotic promoters, is important to note that is not contained in the majority of promoters. One study found less than 30% of 1031 potential promoter regions contain a putative TATA box motif in humans. In "Drosophila," less than 40% of 205 core promoters contain a TATA box. When there is an absence of the TATA box and TBP is not present, the downstream promoter element (DPE) in cooperation with the initiator element (Inr) bind to the transcription factor II D (TFIID), initiating transcription in TATA-less promoters. The DPE has been identified in three "Drosophila" TATA-less promoters and in the TATA-less human IRF-1 promoter.