In eukaryotic systems, the process of initiating transcription from protein-coding genes requires the presence of RNA polymerase II and a broad family of auxiliary transcription factors. Such factors can be divided into two major functional classes: the basal factors that mediate the transcription of all Pol II genes, including TFIIA, TFIIB, TFIID, TFIIE, TFIIF and TFIIH, and sequence-specific factors that regulate gene expression. TFIID, one of the basal transcription factors, facilitates the preinitiation complex assembly through direct interactions with the TATA promoter element. TAF9 (transcription initiation factor TFIID subunit 9), also known as TAF9A or TAF II p32, is a 264 amino acid nuclear protein that, is a component of the TFIID complex and is required for cell viability.