Initiation of transcription by RNA polymerase II requires the activities of more than 70 polypeptides. The protein that coordinates these activities is transcription factor IID (TFIID), which binds to the core promoter to position the polymerase properly, serves as the scaffold for assembly of the remainder of the transcription complex, and acts as a channel for regulatory signals. TFIID is composed of the TATA-binding protein (TBP) and a group of evolutionarily conserved proteins known as TBP-associated factors or TAFs. TAFs may participate in basal transcription, serve as coactivators, function in promoter recognition or modify general transcription factors (GTFs) to facilitate complex assembly and transcription initiation. This gene encodes one of the smaller subunits of TFIID that binds to the basal transcription factor GTF2B as well as to several transcriptional activators such as p53 and VP16. In human, TAF9 and AK6 (GeneID: 102157402) are two distinct genes that share 5' exons. A similar but distinct gene (TAF9L) has been found on the X chromosome and a pseudogene has been identified on chromosome 19. Alternative splicing results in multiple transcript variants.
