Diverse transcriptional functions of the multisubunit eukaryotic TFIID complex.

Each eukaryotic promoter contains a unique array of DNA elements which bind specific transcriptional regulators (1).These promoter-specific factors, which include Spl, CTF, Ga14, USF, AP1, ATF, Octl, and many more, must in some way communicate with the basal transcription machinery (TFIIA, -B, -D, -E, -F, -G, and RNA polymerase 11) which is thought to be common to most, if not all, promoters of mRNA coding genes (illustrated in Fig. 1) (2).The basal factor TFIID is thought to be the key link between promoter-specific activators and the RNA polymerase I1 basal initiation machine (3-8).However, despite an intense effort, the molecular composition of the naturally occurring TFIID from higher eukaryotes and its role in basal and regulated transcription initiation remain a mystery.In this minireview we discuss the possibilities that the endogenous TFIID is a heterogeneous multisubunit complex and that different TFIID complexes play distinct roles in coordinating gene expression in eukaryotic cells.